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Stem Cell accessory bag

Lightweight stem-mounted padded bottle bag for gels, water bottle, camera, Mytimug and other riding equipment; UK-made to last

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Refuelling with an energy gel, taking a swig of water, capturing a sunset on camera… Some things just can’t wait until you hunka down for the night.

Stem Cell provides easy-to-access, protective storage space for the stuff that you’ll need frequently during your ride.

Constructed from waterproof VX21 fabric with a minimalist design in our UK factory, with protective padded walls to protect your stuff, Stem Cell is made to endure the demands of life on the road without compromising on weight.

A webbing ladder offers endless attachment points around the flight deck; simply cut the VELCRO® strap provided to size.

Drawcord closure creates a 5 cm extension tube to fit a 600 ml bottle or 750 ml Nalgene; the Stem Cell also fits a Mytimug 650 (it’s a snug fit).

"Is it waterproof?"

Although highly weather resistant, this product is not fully waterproof due to its stitched construction and drawcord closure. If you are carrying valuables or electronic equipment, make sure to put it in a dry bag. 

Key features
  • 25 Year Alpine Bond
  • Easy-to-access storage
  • Made to last in the UK
  • Fully customisable (contact support@alpkit.com)
  • Made with waterproof and highly abrasion-resistant fabrics
  • Minimalist design for lightweight storage
  • Elasticated drawcord closure maximises capacity
  • Padded walls protect your stuff
  • Bar-tacked webbing ladder for endless attachment points
  • Attaches to either side of stem
  • VELCRO® strap provided
More images
  • Stem-cell-size-comparison - Stem Cell vs Stem Cell XL
  • Stemcell packed - See what you can fit inside your Stem Cells
  • Stemcell swig750 - 750 ml drinks bottle can be accommodated in Stem Cell
  • Stemcellxl packed - Pack your Stem Cell with MytiMug 650, 125 ml gas canister, Kraku and Snapwire
  • Stem-cell-on-bike-double -
  • Stem-cell-on-bike-side -
  • Stem-cell-on-bike -
Vital stats

Fabric: VX21
Stitched Seams
Elasticated drawcord closure
VELCRO® strap


Weight: 63 g
Width: 9 cm
Min height: 15 cm
Max height: 20 cm

Origin: United Kingdom

Product Care Information

Stem Cell has a C6 DWR coating which helps it to repel water and dirt. After your two-wheeled epic, wipe down your Stem Cell with a damp cloth to remove dirt.


A 4-layer, 210 denier laminated nylon fabric with a DWR finish: VX21 (or X-Pac to its friends) is a high tech, ultralight sandwich of materials that is highly abrasion and tear resistant, low-stretch, and waterproof.


UK Made Adventure - Stem Cell

An insight into the creation of a bike packing set up here at Alpkit HQ UK factory. The Stem Cell.


6 Fat Tyres…and Lee’s 2 feet.

Gearing up for the 150 mile Rovaniemi arctic ultra on bike and on foot.


Bikepacking links

Need some inspiration for suitable trails to ride, people to follow or events to enter.. here are some suggestions.


Long Mynd delights

Pedal powered peace, the charm and beauty of the Shropshire landscape


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Free UK Shipping on all orders

Free 2 day delivery to UK addresses is included in all orders so the price you see is the price you pay. Upgrade to next day at the checkout.

Free No hassle 123 Day Returns

Buy with confidence and if you are not happy, change your mind or want a swap for any reason then return it for free and we will exchange or refund no question. The price you see is the price you pay. Just return the kit as you receive it - in its original condition, unused, unworn, with original packaging and fit for resale.


We offer a range of finance options from 0% to 9.9% starting on orders over £500. Please give us a call on 01773 417007 to apply for finance. Our customer support heros will take your order and talk you through the quick and easy application process.

Alpine Bond

If one of our products does not meet your expectations upon delivery or, if it does not live up to the demands placed upon it, please return it within 3 years of purchase for repair, replacement or refund. If the problem is our fault then we will do this to your satisfaction if it’s your fault then we will help out the best we can.


5 Reviews


Used this product?

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Bought one of these for a trip last year. Just popping an order in for another to expand my cockpit storage space. Good work once again Alpkit!

amazing little bag

Use this bag fulltime for commuting use carrying my phone and battery charging stuff (Cinq - Son hub). For bigger tours the GPS will also fit.
Only used it for road use and very light offroad and it kept the contents well. Even in rain the phone stayed quite dry

Thomas O'Moore
great little bags.

I use two of these up front to help disperse some weight and keep handy bits ... handy.. smile.

I have in the past put two 1 ltr Nalgene bottles in them with no problems as I had a full size frame bag. The draw cord fits perfectly tight and snug just under the Nalgene screw lid which is fine as there's no need to have these fully enclosed as its just water bottles.

More often than not though now I have ditched the full size frame bag off my Sonder Camino Ti they are used for bits and pieces i require handy.

I will upgrade to the waterproof versions soon I think.

Andy Pryke
Great bit of Kit

Have used this on a number of occasions, and no its not waterproof, but its really handy!

Its round shape means its great for items, easy to dip into when riding, bags of nuts etc, I have a dry version, which I don't rate - More work on that one guys
Drops a point due to the velcro

Let's design a great outdoors bag then stick a hole in the top for the rain to get in

As above.
Love Alpkit gear but my sister bought this for me at my request for xmas pressie a few years ago and I saw the flaw straight away so have never used it.
Great bag but if there is a hole in the top to let the water in then is crap for UK use or any other country where it rains.
Am very surprised it is still sold now. Have the Alpkit people actually used it for storing their snacks in the British climate?
Storing anything other than a plastic bottle in this is pointless.