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Mr. Fusion Seat Pack

(3 customer reviews)

$230.00 – $275.00

Large capacity waterproof seat pack system. Complete with integrated mini-rack and large-volume, removable drybag.

The same holster will fit either a 12L or 15L max capacity drybag, depending on the trip and necessary volume requirements. The 15L is an extra large bag please check the clearance measurements to make sure it will fit. For reference it’s more than double our sewn Foxglove Saddlebag.

The complete system includes:

  • 4130 Chromoly mini-rack (built by Hunter Cycles in California, USA)
  • Full Hypalon lower holster section
  • Waterproof proprietary RF-welded 210D PU-coated nylon drybag
  • CNC’d 6061 aluminum seatpost clamps or non-marking nylon clamps for droppers shafts

Mr. Fusion is our modular waterproof seat pack, centered around a svelte mini-rack, holster, and a dedicated seat post clamp. 100% waterproof, and with the snap of one buckle, it’s insanely easy to load & unload.  Pack your things off the bike, and never worry about wiggle, wobble, or sag.

We offer machined collars to clamp the shaft of your seat post in sizes 27.2, 30.9, or 31.6 mm. If you have a smaller 25.4 mm seat post you can get a shim to size up to 27.2 from amazon.

If you have a dropper post, select the seat post size of your dropper and you will receive a non-marking nylon clamp and rubber protector for your dropper shaft. Nylon dropper collars for 31.6 droppers will be available fall 2024.

Standard Features Include:

  • 560g complete (including drybag, rack, seatpost clamp, and all hardware)
  • PU-coated 420D fabric in our signature LightBlack™ color
  • HDPE Stiffened side panels to avoid thigh rub
  • Bartacked at all critical stress points
  • Duraflex™ acetyl buckles throughout
  • Full stainless steel rack attachment hardware included
  • Double-back main seatpost attachment
  • Convenient, integrated dangle points
  • Handmade in Calgary, Alberta Canada

Clearance Requirements

  • Mr. Fusion with 8-12L drybag requires 8″ between seat rails and tire (when rear suspension is fully compressed on FS bikes), and 4.5″ of exposed seatpost.
  • Mr. Fusion with 10-15L drybag requires 9.5″ between seat rails and tire (when rear suspension is fully compressed on FS bikes), and 5.5″ of exposed seatpost. This is a BIG seatpack.

♦ NOT recommended for carbon seat posts or posts with elastomer suspension. 

 

Additional information

Weight 1.2 lbs
Weight

19.7 ounces (560 grams). Exact weight depends on features selected.
Volume

8-12 Liters for the Large dry bag.
10-15 Liters for the XL dry bag.
Compatibility

Large dry bag requires 4.5" of exposed seat post and 8″ of clearance between the saddle rails, and the tire at its closest point to the saddle.

XL requires 5.5" of exposed seat post and 9.5″ of clearance between the saddle rails, and the tire at its closest point to the saddle.

Not compatible with carbon posts, suspension posts, or dropper posts. Please see FAQ tab for explanation.
Dry Bag Dimensions

Large dry bag is 28.5" x 12.5" when laid flat, XL dry bag is 28.5" x 13.25" when laid flat

FAQ

Q : How do I know what size seatpost clamp to choose with my order?

A : Mr. Fusion mounts directly to the seatpost, not to the bicycle frame itself.  So, you will want to choose the clamp size that is the same diameter as the seatpost that your bicycle uses.  Often, if you remove the seatpost from the bicycle frame, the seatpost size will be stamped or etched into the seatpost, near the base.  If your seatpost reads something like “27.2mm x 400mm”, this means your seatpost is 27.2mm in diameter, and 400mm in length.  You would want to choose a 27.2 clamp for your Mr. Fusion order in this scenario.
Q : Is Mr. Fusion compatible with a dropper post?
A : Yes. Please select the dropper post size in the drop down menu. 
Q : Why is Mr. Fusion not recommended for carbon seatposts?
A : Some folks tend to get a bit ham-fisted when tightening bolts on their bicycles, and Rockgeist cannot be held responsible for damage to expensive carbon seatposts, due to over-torquing of the clamp bolt.  The clamp bolt is meant to be tightened to NO MORE than 4Nm.  This is about the same torque that you would apply to MTB brake levers; tight enough to hold the stabilizing rack in place reliably, but not so tight that the rack cannot rotate on the seatpost, in the event of a crash. If you do decide to install Mr. Fusion on a carbon seatpost, this is done at your own risk.
Q : Is Mr. Fusion compatible with a suspension seatpost?
A : No.

Q : Can I use both drybag sizes in the same Mr. Fusion holster?

A : Yes!  Mr. Fusion uses the same holster for both drybag sizes.
Q : How do I know if I have the required clearance and exposed seatpost for Mr. Fusion with a 12L drybag?
A : For Mr. Fusion with 12L drybag, you will need 8″ of clearance between the saddle rails, and the tire at it’s closest point to the saddle.  You will need 4.5″ of exposed seatpost (measured from the saddle rails to the top of the seatpost collar on the bicycle frame.  Keep in mind that if you ride a full suspension bike, these measurements need to be taken when the suspension is fully compressed.
Q : How do I know if I have the required clearance and exposed seatpost for Mr. Fusion with a 15L drybag?
A : For Mr. Fusion with 15L drybag, you will need 9.5″ of clearance between the saddle rails, and the tire at it’s closest point to the saddle.  You will need 5.5″ of exposed seatpost (measured from the saddle rails to the top of the seatpost collar on the bicycle frame.  This is a BIG seatpack!  Keep in mind that if you ride a full suspension bike, these measurements need to be taken when the suspension is fully compressed.
Q : My Mr. Fusion drybag has developed a hole.  How should I repair it?
A : Most common outdoor gear repair kits, designed for PU-coated fabrics, will work well on the Mr. Fusion drybag. Tenacious Tape, or similar gear repair tape, is also a good option for field repairs.  If you would like us to professionally repair your Mr. Fusion drybag with a welded-on patch, please email [email protected].

Instructions

Rockgeist Mr. Fusion Installation Instructions

Thanks for choosing the Rockgeist Mr. Fusion seat system! Installation is a bit different than other seat packs on the market. Please follow these instructions carefully, to ensure the best performance from your seat system. 

Step One: Separate the two main cradle parts by unlacing the side compression straps from the ladder lock buckles on the lower cradle. (For safety in transit, and to show you how they attach, these two pieces are shipped assembled.) 

Next, install the upper cradle onto the seat post, using the black rubber velcro strap. It should look like this: 

 Step Two: Lace the webbing “ears” which contain the plastic flat loop, over the seat rails like this: 

Step Three: Install the seat post clamp onto the seat post. You must take the seat post out of the bike frame and slip the collar onto the post, then put the seat post back into the bike frame. 

Position the collar 4.5” (11.5 cm) down from the rails for use with the size Large dry bag or 5.5” (14 cm) for use with the XL dry bag.  

Torque the nylon lock nut to no more the 3 Nm using an Allen key and a wrench. This torque is enough to hold the system in place, but will also allow the rack to rotate on the seat post in the event of a crash. 

Things should now look like this: 

 Step Four: Lace the long, side compression straps through the flat loop in the webbing “ear” in the top cradle, then through the ladder lock buckle in the lower cradle. Keep the lacing loose to help with packing of the dry bag. Lacing should look like this: 

Step Five: Insert the included dry bag with the welded seam of the bag in the vertical orientation. (Pack the dry bag with your gear before inserting into the holster). Clip the rear strap over the dry bag and tighten. Tighten side compression straps by pulling up on the grab loops. Enjoy your ride! 

3 reviews for Mr. Fusion Seat Pack

  1. Hannah S. –

    This seatpack is a game changer! No matter the surface, things stay dry, stable, and don’t sway. Rockgeist has great customer service as well, and they promptly sent us new dry bags after realized the ones they sent us weren’t properly welded (way before we would have noticed!). Highly recommend the Mr. Fusion and anything Rockgeist offers.

  2. Jacob Kruse –

    The Mr. Fusion is genre defining for the bike packing seatbag category. The design is so good, the integrated drybag and minimal rack system work so well, it is a joy to use. It always works, has never slipped or shifted on rough terrain. 100% recommend this product.

  3. Sepie Moinipanah (verified owner) –

    My partner and I recently bought a pair of Mr. Fusion Seat Packs for our bikepacking trips this summer. To kick things off, we set these up on our bikes (actually shown above in one of the pictures!) and rode about 50 miles in each direction on mostly paved roads, with some gravel thrown into the mix. We were very pleased as to how well they secured our belongings and after a while, we barely noticed that they were there. The weight distribution is key but the part that really blew us away was the lack of swaying we felt, especially while cornering.

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What Packs Best in Mr Fusion?

Mr. Fusion is a great place to pack compressible items that can’t get wet; down sleeping bags, puffy coat, extra clothes, etc. 

Go the Distance

Read Bikepacking.com’s long term review from 2016. Great insight on the history of this bag designed by Porcelain Rocket.

5,000 Mile Review

Not only is it completely waterproof, but the mini-rack/holster system prevents sway and movement better than any other seat pack on the market.

Logan Watts

Mr. Fusion also works with dropper posts

An Innovative History

This product was developed by Porcelain Rocket; a Canadian company widely credited as being pioneers in the modern era of bikepacking bags. Today, Rockgeist continues the legacy of Porcelain Rocket by partnering with them to manufacturer their welded, waterproof designs.