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FastBack Carbon Slim Seatback Bag

5 reviews
SKU: FBS095.1

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The FastBack Carbon Slim Seatback Bag is the one stop shop for hard-shell seats. Are you going to ride until the sun sets? Toss a jacket in the Carbon Slim. Gonna work up an appetite climbing that mountain? Fill the Carbon Slim with GORP and Clif Bars and you're set. Forgot it's Mother's Day? Grab some chocolates and a card and make haste! Our SpiderGrip technology is reconfigurable to achieve an exact, secure fit every time. Once you form the pocket to the shape of your seat, you can take it off and put it back on without any trouble at all. The FastBack Carbon Slim Seatback Bag will let you ride farther and ride faster.


1. Why this bag?

The Carbon Slim is a simple, well made, nice sized bag. It's not huge- we call it the Slim, after all- but it can easily carry lunch, a jacket, and some tools. It's made from sturdy coated coated nylon with a waterproof zipper. It fits all kinds of seats, and works well if you have your seat reclined way back.

2. Will it attach to my seat?

If you have any carbon or carbon like width seat, the answer is YES. With the unique SpiderGrip harness, it doesn't matter how rounded or squared off the top of the seat is, what the width is, or whether you have a headrest or not. It just conforms and fits. Secure, no sloshing around, and yet easy to move from bike to bike.

3. How does it work?

It's super simple and super effective. A special Velcro brand velour panel lays on the front of your seat near the top. Six velour Velcro straps wrap around from the back and stick- quite firmly- to the panel. You form the straps around the seat and they lock into the panel, taking whatever the shape of your seat is. It basically forms a custom molded pocket around the top of your seat.

4. After it's molded to the seat, can I easily take it off?

Yes. If you mold it tightly to the seat, it may be difficult to remove without unstrapping probably one or both of the lower straps. If you mold it not so tightly, you should be able to slip the bag on and off the top of your seat when you want to.

5. How big is it?

Approximately 12" x 10" x 4" (30 x 25 x 10cm). You can also add an optional Tool Pouch to the back for additional carrying capacity. You can also use the webbing strips and Velcro panel on the back for attaching/lashing on other things.


Initial forming of the harness takes a couple of minutes. After that, you can install and remove the bag in seconds.

How to form the harness to your seat:

  1. Unstrap the velour panel from the bag.
  2. Lay the panel on the front of the top of your seat. Center it up on the seat with the top of the panel about 2 inches (5cm) down from the top of the seat. It can go over or under your seat pad, your choice.
  3. Place the bag against the back of the seat, with the top even with the top of the seat.
  4. Wrap the two top straps over the top of the seat and down onto the velour panel. The straps are velour on top but have tiny molded hooks on the back, and will fiercely grip the panel. "Roll" the straps down onto the panel, forming them to the edge and face of the seat as you go.
  5. While gently pulling down on the bag, pull the next pair of straps around the seat and onto the panel. Repeat with the bottom pair.
  6. Depending on how tightly you've pulled the straps, you may or may not be able to remove the bag by pulling it up and off the seat. Adjust the strap tension as you like it. It will be easier to take the bag on and off if the velour panel is under the seat pad.


  • Made in Portland, Oregon USA of mostly Made in USA materials, by people who like to sew and are paid a living wage to make things. Unique, super versatile SpiderGrip harness, waterproof zipper, and heavy duty waterproof nylon packcloth. We don't call it "waterproof" because water will get in if you submerge it, but it will hold off a rainy day pretty darn well.
  • Has a white high reflective strip across the back, and a couple of webbing strips and a Velcro pad designed for attaching other things to it. We make an optional Tool Pouch that grabs on to the back and expands the carrying capacity.
  • SpiderGrip harness forms to the top of your seat and grips great regardless of the seat shape, including difficult to attach to seats like the HPVT BodyLink.
  • Urethane coated nylon, #5 waterproof zipper with nylon loop pull tabs. Velcro brand straps and panels.
  • Size approximately 12" x 10" x 4" (30 x 25 x 10cm). Optional Tool Pouch for additional carrying capacity. Webbing strips and Velcro panel on the back for attaching/carrying other things.
  • The harness on this bag is extremely versatile and will form nicely to any narrow-ish recumbent seat. It is not intended for regular, full width mesh type seats. It works great on narrow mesh seats like the Euromesh and the Hoagie though. It can be used on Challenge metal seats and hard to attach to seats like the Zephyr and BodyLink.
Customer Reviews
4.8 Based on 5 Reviews
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Filter Reviews:
Burkhard B.

FastBack Carbon Slim Seatback Bag

It fits perfectly to my HP Streetmachine and can carry the things I need like passports, keys, smartphone, some tools etc. Well made.

A T-Cycle Customer
Will T.
United States United States

Perfect fit

Just the right size, & a perfect fit on my hard shell seat. Might be a bit tight against the rear wheel fender at a lower seat angle, but at 40 degrees on my performer jc70 it’s a winner.

Mark R.
United States United States

Fastback Carbon Slim Seat Bag

I have an ICE SprintX with hard shell saddle. I have “banana bags” for hauling larger items such as cool weather layers etc. Needed just enough space for tire repair kit, small tools, spare tubes, eyeglasses case. This bag fits the bill. It has rubbed the rear tire a few times if I try to fill it to capacity. (700c) which is my only complaint. It also seems quite pricey bumping close to $100 but it is very well made and designed.

T-Cycle FastBack Carbon Slim Seatback Bag ReviewT-Cycle FastBack Carbon Slim Seatback Bag ReviewT-Cycle FastBack Carbon Slim Seatback Bag Review
Allen D.
Sacramento, USA

Fits Perfectly

I bought this at AlphaBent in Sacramento for my Trice S trike. It fits the ICE hardshell seat perfectly and holds a 1.5 liter Camelbak water bladder perfectly. And there's room for a pump, tire repair kit, a couple of tools and my phone.

Scott B.
Saint Louis, USA

FastBack Carbon Slim

I own an M5 carbon high racer. There is not much clearance between the seat back and rear tire. I have been looking at a variety of 'wedge' packs but the wheel proximity was an issue. The radical designs pack, which is really two packs joined with webbing, looked like I hung two sacks off the back of my seat. The fastback carbon slim setback bag was a perfect solution. Though it does not have 10+ liters capacity like the wedges, it more than has enough capacity to carry two tubes, a repair kit, a .25" thick locking cable, tire tools, wallet, phone, headlight, and still have considerable unused volume. The pack precisely fits the back of the seat and the mounting system is quite secure and unobtrusive. I was prepared to spend $200 or more on a wedge pack, but given the functionality of the fastback product I doubt that I shall do so.