Bikepacking Seat Pack Evolution + 3 Seat Bags Compared

A look at the history and evolution of bikepacking seat bags and a comparative review of the Revelate Terrapin, Porcelain Rocket Mr. Fusion, and Bedrock Coconino… plus a sneak peak at the all new Mr. Fusion dry bag system.

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For those unfamiliar, the seat pack is that curious stuffed missile that get’s strapped under the saddle at the rear of the bike. Its placement is inspired by traditional saddle bags, such as the classic canvas designs by Carradice, but the seat pack is designed for more rugged use and its structure is a bit more streamlined as a result. This was a revolution to ultralight multi-day mountain bikers who are able replace the typical below-the-saddle tool bag and carry much more gear in a way that’s significantly lighter and more aerodynamic than traditional panniers.

For those who are familiar with this piece of gear, the Viscacha, by Revelate Designs, might come to mind as one of the originals. According to Revelate’s Eric Parsons, “Jeff Boatman and I were the only people making bags back then. Who was first to make bikepacking seat bags – Jeff, he started in 2006 I believe, I started in 2007. I was doing my own thing in AK influenced by the needs of winter bikepacking races and got pulled into modern bikepacking later due to the rise of the Colorado Trail Race and the Tour Divide.”

The first bag I made was called the ‘Super Twinkie’ in 2007, it was bigger than the Viscacha but lacked any structure. A lot of people used them in winter fat bike races here and the arrowhead. The Viscacha came about in 2009 and the core design has been unchanged since then, aside from tweaks.”

The seat bag has progressed quite a bit since 2007. Designs changed in size to meet riders’ needs, and now there are a few unique systems out which allow the bag to quickly disengage from its harness, making packing and unpacking much easier. Here are three bags we’ve tested that push the seat pack in new directions:

Bedrock Coconino with RailWing - Bikepacking Seat Pack

The Bedrock Coconino & RailWing

The Bedrock Coconino with RailWing was conceptualized by and designed in collaboration with Joey Ernst from Velorution Cycles. The goal was to create an incredibly stable seat bag that can be removed from or loaded back on the bike in less than a few seconds.

Bedrock Coconino with RailWing - Bikepacking Seat Pack

The RailWing is a simple machined aluminum bracket that clamps onto the saddle rails. The intent of the RailWing is twofold, the first of which is to prevent ‘tail-wag’, which is the phenomenon that comes from pedaling with a large seat pack load, resulting in the bag swaying in a back and forth motion. The second is to enable the quick release of the bag for packing and unpacking.

  • Bedrock Coconino with RailWing - Bikepacking Seat Pack
  • Bedrock Coconino with RailWing - Bikepacking Seat Pack
  • Bedrock Coconino with RailWing - Bikepacking Seat Pack

The bag has a roll-top enclosure and a velco strap that secures it to the seatpost. The RailWing has two locking compression straps that affix to the bag. One perk of the RailWing is that there is not much that could bend or break in a crash; it’s a solid piece of metal. And the Coconino can function with or without the RailWing so you are never dependent on any hardware.

Bedrock Coconino with RailWing - Bikepacking Seat Pack

  • Bedrock Coconino with RailWing - Bikepacking Seat Pack
  • Bedrock Coconino with RailWing - Bikepacking Seat Pack
  • Bedrock Coconino with RailWing - Bikepacking Seat Pack

Let it be known that we haven’t taken the Coconino to the ends of the earth and put it through rigorous testing, but on initial rides and use, it’s an impressive and well-built seat bag with nice details such as locking compression clips. The main body of the bag is made from quality materials such as X-pac, and more durable heavy gauge fabric at the contact points. The RailWing is an interesting innovation that noticeably stabilizes the bag and serves as a very handy quick release and loading mount. It should be noted that the RailWing can also be retrofitted to work with the Revelate Viscacha or Pica.

Porcelain Rocket Mr. Fusion Seat Pack, Bikepacking

Porcelain Rocket Mr. Fusion Seat Pack

The Mr. Fusion is Porcelain Rockets’s solution to ‘tail wag’. The system combines the stability of a traditional rack with a low profile design, modular harness system, and modern materials. Think internal frame backpack. The system has three parts: the rack with fabric harness, the upper harness piece with top clips, and the bag itself. The rack attaches to the seatpost via a custom machined aluminum collar. The bag has a roll-top enclosure and a velcro loop that lashes to the seatpost for added support. Two compression straps hug the sides and a single compression strap battens down the rear of the bag. With the rigid rack and the well designed compression points, there is absolutely no movement in the system, even on the rough stuff.

  • Porcelain Rocket Mr. Fusion Seat Pack, Bikepacking
  • Porcelain Rocket Mr. Fusion Seat Pack, Bikepacking
  • Porcelain Rocket Mr. Fusion Seat Pack, Bikepacking

Obvious benefits of the Mr. Fusion system include its rock solid stability, the ease of removing the bag for packing, and the ability to customize your bag from an array of colors and fabrics. A couple of hidden perks are the ability to utilize the rack to lash on additional items, such as a spare tube, or a tent ground sheet.

Mr. Fusion V2

Porcelain Rocket Mr. Fusion Dry Bag System

Version two of the Mr. Fusion (pre-production model shown above and below) features a radio frequency welded (RF) drybag and a slightly tweaked harness. The rack is the same but the upper harness is slightly different with internal panels which serve to stabilize and contain the load. Porcelain Rocket hopes to have the production sequel ready by late-August and it will retail for $185.

  • Porcelain Rocket Mr. Fusion Dry Bag System
  • Porcelain Rocket Mr. Fusion Dry Bag System
  • Porcelain Rocket Mr. Fusion Dry Bag System

Revelate Terrapin Bikepacking Seat Pack

The Revelate Terrapin Seat Bag

The Terrapin by Revelate Designs is a holster-like mount that accepts the Revelate drybag or similarly shaped load. With the Revelate dry bag, the system is 100% waterproof and the bag can be quickly removed from the bike for ‘in the tent’ packing or unpacking. Out of all of the seat packs explored in this review, this one has gotten the most use.

  • Revelate Terrapin Bikepacking Seat Pack
  • Revelate Terrapin Bikepacking Seat Pack
  • Revelate Terrapin Bikepacking Seat Pack

The key to the Terrapin is it’s compression system and internal structure. It features a stiff plastic bottom and side sheets which helps lessen, although doesn’t completely eliminate, sway. The fiberglass stiffened sides prevent outward bulging with an unwieldy load. The lower compression straps feature an upward pull which engages the side panels, yielding an intricate compression that perfectly secures and shapes the load within the harness. The rear compression strap loops around a sturdy red loop and allows maximum lateral compression.

Revelate Terrapin Bikepacking Seat Pack

Out of all of the seat packs tested here, the Terrapin is the easiest to access and remove the bag. It also has an added benefit of allowing additional items, such as a tyvek ground cloth, to be nestled within the harness. Another impressive feature is the rugged design of the seat rail attachment (shown above in the middle photo).

Bikepacking Seat Bag comparison

Side-by-Side Comparison


The weight difference of these systems is fairly negligible, in my opinion. Here are the manufacturers’ claimed weights:

  • Bedrock Coconino 14.6 oz / 414 grams
  • Revelate Terrapin 17.5 oz / 496 grams (w/Drybag)
  • Mr. Fusion 13 oz / 369 grams

Bikepacking Seat Bag comparison

Carrying capacity and size

All of these bags are adjustable and can be overstuffed, or rolled and cinched for a small load. The Terrapin is slightly larger capacity than the others, and the Coconino is the must streamlined with a tapered front that might be preferred by some who complain of thigh rub.

  • Bedrock Coconino 6-12 liters
  • Revelate Terrapin Up to 14 liters
  • Mr. Fusion 5-13 liters

Bikepacking Seat Bag comparison


  • Bedrock Coconino $175
  • Revelate Terrapin $125 (w/drybag)
  • Mr. Fusion $175


Which bag is our top choice, you might ask? Well, all three are excellent options (or else they wouldn’t be here); each has its particular strength and is fit for specific conditions. The Bedrock Coconino is a solid choice for those looking to travel light and fast. It has the most streamlined design and might also be a good fit for smaller riders who have limited space between the saddle and rear tire. The Revelate Terrapin is the least expensive and as of right now, the only one available that’s fully waterproof. It’s also the largest, and in my opinion the easiest to use with regard of removing and reinserting the bag. The Mr. Fusion is an excellent choice for long term expedition travel where rugged dirt roads and trails are the preferred terrain and sway is a concern. It is by far the most stable and also has the option to use the rack for additional storage. The version two production model will be fully waterproof as well.

While all three of these seat packs are incredible, my guess is that we’ll see even more innovations as bikepacking progresses. Stay tuned.

  • Christophe Noel

    I have used the Coconino bag for the last three seasons and love it. I’m now using the updated iteration with the RailWing, and it’s a huge improvement. I have really tortured my Coconino and it has held up exceptionally well. I also started using the Mr. Fusion last March and agree it is without question the most stable bag I’ve ever used, and I’ve used many. My only grouse with both of the above bags is the velcro at the mouth of the bag opening. I’ve shredded a lot of gear passing it by those little scratchy teeth.

  • I am glad you mentioned your beef with velcro on the bag opening. I agree one hundred percent and intended to add that in the review; it must have slipped my mind while writing. That is one of the plusses in the Terrapin camp… the Revelate Dry bag is velcroless. For what it’s worth V2 of the Mr. Fusion should also work with the Revelate Dry bag.

  • Christophe Noel

    I like to use my base layers as little gap-fillers when trying to maximize the volume of my seat bag. On my last trip I was a little spacey-headed and stuffed my brand new Icebreaker wool top into my bag and snagged the hell out of it on the Mr. Fusion velcro. I’m glad I travel alone. The tantrum would have been embarrassing otherwise.

  • Anarchitech

    Personally, I find the provided seat rail attachment on my Revelate Pica to be a pain to use in practice. It’s easier to hook up with the bag empty. I’ve fabbed up an attachment similar to the Rail Wing and it helped. And, if you are on a budget, you can pick up a SealLine or other drybag, attach the clip around your seatpost just below the top tube, and tie the bag up to the seat rails with a webbing strap or bandana. If you’re feeling crafty, you can glue wear patches to the bag where it contacts the metal bits of the bike. Cheap, dry storage, and I’ve never had much trouble with “sway” as long as heavy objects are packed toward the seat tube. I’ve used 10 and 15L bags like this for years; bought the Pica this year to see what all the fuss was about. I would agree that the Revelate is well built, and access to a rear opening bag is an improvement over the “hobo dry bag hack,” however the seat rail attachment gets a C- or D in my book. YMMV. PS: Great site, Logan.

  • With respect to sway, is there a noticeable difference between the Terrapin and the Mr Fusion? Also would a dry bag such as they offered by Sea-to-Summit [ok I might one to many of these :) ) work okay with the Terrapin?


  • There is. The Mr. Fusion pretty much eliminates sway while the Terrapin simply lessens it (in comparison with its predecessors, such as the Viscacha). Most drybags should work if sized correctly. The Revelate bag is very nice though.

  • Thanks.

  • Vik Banerjee

    I’ve used the Mr. Fusion for all my trips this year. The stability is great and the ease of loading/unloading makes camp setup a snap. It was a nice addition to my bikepacking rig. :)

  • uberwald

    I’d like to see someone compare these against one of the older style bags, like the Carradice Camper :)

  • I agree… thanks Vik!

  • The Carradice Camper Long Flap is a great bag… I used a similar design in Africa last year. Completely different experience though.

  • uberwald

    …and that’s why it would be an interesting comparison for an article. Most of us don’t get to try 30 different bags before we pick the one that matches our riding style.

  • I think the biggest and most obvious difference is how the bags handle the rough stuff. A carradice is going to fly up, bounce around, etc (unless you have it secured to a rack, which is almost required). These seat bags are made to withstand rugged trails, and remain secure. Also having a rack adds additional weight (not to mention the fact that a waxed canvas bag is much heavier that a bag made from VX21 and Cordura).

  • Jacob Copple

    Any say in the clearance for each bag? Maybe I’m missing it, but I can’t find any measurements here or on their respective sites.

  • It all depends on the height you have your seatpost adjusted, and what size tires/wheels you are running. The smallest one is the Coconino. My wife is 5′ 7″ and has used the Mr. Fusion on a Pugsley with 4″ tires.

  • Christine Tabor

    Can I put one, like the Terrapin, on a road bike for a short, weekend trip – onto a carbon seatpost?

  • Hi Christine. Sorry for the delay; just flew back from Vegas. Yes, either the Terrapin or the Coconino will work. You have to make sure you have enough clearance between your seat and tire though. How tall are you and what size tires?

  • Mark

    Have any of these been tried with a dropper seat post?

  • I know Gabe rigged a nice hack with the Mr. Fusion. Check out the photos on the Three Sisters Three Rivers route in Oregon (in the bikepacking routes section). I have used the Viscacha with a dropper, but I have really long legs, so there is room to spare. I think the Coconino would allow a couple inches on a hardtail if you have really long legs as well.

  • Daniel

    Absolutely love the idea of mounting the Mr. Fusion on a rack mount seatpost collar. In fact I think that’s going to be the reason I pull the trigger on one. Thanks for the clever hack!

  • The one issue with that solution is the bolts tend to rattle loose. So if you go that route, use loctite. Scott’s seat post mount that ships with it works better as it has a through bolt…

  • Michael Viglianco

    Do you prefer the style with the removable dry bag? I can see the advantage but I can also see it being annoying to stuff the bag and then try to stuff the bag in to the holster thing? It seems just stuffing stuff in to a single bag already on the bike could be more convenient…..or not.

  • I love the removable bag. For me, I pack clothing in it and it’s a matter of one or two clips, pulling out the bag and throwing it in the tent. Then the bag get’s packed the next morning in the tent and slid into the holster. To me it’s the easiest solution out there. Another bonus is when staying in a hostel, the drybag can be hung on a coat rack or bed post. The Mr. Fusion V2 is the easier and more stable of the two, but the Terrapin drybag is a little burlier. The ability to electrical tape a spare tube on the bottom of the MrF ‘rack’ is another perk.

  • Michael Viglianco

    I can see why the new Terrapin with the valve for compression would be nice for clothes. . I’m not really solving for the most stable for aggressive terrain but more for the ability to put all of something in there. All clothes, or all sleeping, etc..Another nice thing about the new version of the Terrapin is the place for hanging a blinky light.

  • If you are kicking around those two, I would make the decision based on how much weight you plan on having. The MrFv2 handles heavy very well, and the Terrapin can get saggy if loaded long and sloppily with heavier clothing and things.

  • Donnieboy

    They’re kinda apples and oranges in the sense that the carradice looks great and keeps your stuff stored in an urban environment (paved roads). When you hit bumps you need more security like what you would get from a tight closed, multiple point of attachment compression system (most bikepacking bags).

  • uberwald

    I really would rather see an actual comparison article instead of just the assurances that they’re different. If you have the resources to make the comparison (the ability to try the different styles including a carradice style bag), then it’s just laziness in not writing the article. If you don’t have the resources to make the comparison, then I really wish you wouldn’t waste my time.

    I still would love to see a comparison.

  • Conor Phelan

    Hi Logan, as a follow-up to Mark’s question…on my girlfriend’s full-sus stumpjumper, if she didn’t lower her dropper post at all during a trip, would the Coconino attachment in anyway damage the dropper post if the bag is attached around the sliding inner post, or would that be a non-issue? Thank you

  • Hi Conor. It shouldn’t be an issue. You could always apply some electrical tape, or a product called ‘Shelter’ if you are worried about it.

  • Conor Phelan

    Great, just what I was hoping, thanks again.

  • Manuel Demetz

    Does anybody know a solution that works also fine with a dropper seat post! I’ve used my apidura for a test ride with an e-mountainbike but the construction of the Apidura does not work properly with a dropper seat post! I believe that this would be an interesting solution for offroad/trail bikepacking routes..

  • Check out the Arkel review from last week. Also, Porcelain Rocket is working one as well.

  • Manuel Demetz

    Thank you! I will do that…

  • Manuel Demetz

    The Porcelain Rocket ist not on the market yet, or I am wrong?

  • guest

    wow. Your’e a dick.

  • That is a pretty harsh comment and as to your time being wasted, that is of your own doing. Interestingly you chose to post here for what reason other than to make a pointless rude comment?

    Maybe you could point us to your own reviews so we can see how it should be done.

  • linked1


  • linked1

    Wow, you’re a pro. Kudos for taking the high road with uberdick.

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