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Undersaddle XL Bag

5 out of 5 stars
3 Reviews



Undersaddle XL Bag

When you find your saddle bag zipper is straining to shut on nearly every ride it might be time to invest in a bigger bag. Castelli's Undersaddle XL Bag will hold all of your essentials — plus the extras you can't leave home without — but won't add undue bulk to your frame. Made with water and stain-resistant materials and a water-resistant zipper, the bag has Castelli's expected combination of sleekness and style.

The bag's storage features are rounded off with an internal storage pocket and external mini-pump sleeve. It attaches to your frame quickly and securely with a hook-and-loop strap, and even has reflective accents to help keep you visible to motorists, day or night.


  • Spacious saddle bag for all your essentials
  • Hook-and-loop straps mount bag easily to saddle
  • Zipper opening makes reaching those repair tools fast
  • Item #CST00AI
1 pump
water resistant zipper
6 x 15 x 6 cm
Recommended Use
Manufacturer Warranty
30 days

Overall Rating

5 based on 3 ratings

Review Summary

1 Stars - 0 reviews
2 Stars - 0 reviews
3 Stars - 0 reviews
4 Stars - 0 reviews
5 Stars - 3 reviews

What do you think about this product?


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5 out of 5 stars

April 5, 2021

Sleek, just-big-enough bag

I've used it several times

As other reviews have mentioned, it is not really "XL" when compared to other bags on the market. However, as long as you purchase it knowing that, it's a great bag. I fit a tube, Co2, two levers, a multi-tool and a tiny patch kit in there with no room left to spare. The external pocket for a pump was a pleasant surprise (somehow I missed it in the marketing) and should fit most pumps you may otherwise throw in your jersey.

Anthony A
5 out of 5 stars

November 20, 2020

Awesome Saddle Bag

I've put it through the wringer

Was skeptical about the size of this bag from the images but after receiving and putting all my necessities in and still having a little space while it maintaining its small sleek shape; I've fallen absolutely in love with it. Holds 2 tubes; 3 co2 canisters; levers; multi-tool; patch kit; cards & cash and has room for more. Favorite saddle bag I've owned.

Edward W
5 out of 5 stars

November 18, 2020

Best under seat bag I've used

I've used it several times

A lot of folks apparently feel like "XL" is a misnomer, but I gotta say, I wouldn't want a bigger under seat bag than this. I like it so much that I have two -- one for my tubeless Open, and another for my tube tire bikes. For me, the thing that sealed the deal is the mini-pump sleeve. I love not having to carry my pump in my jersey or on the frame. Aesthetically, it's better looking than anything else I've seen. Functionally, here is what I carry in the one on my tubeless bike: Lezyne compact (11 tool) multitool CO2 valve & cartridge Tubeless plug kit 2oz bottle of Stan's sealant 2 kool stop tire levers 2 Nitrile gloves 28-622 inner tube Lezyne high-volume mini pump (in exterior sleeve) The one for my tube setups has extra room, because it has all of the above minus the Stan's and the plug kit.

user image

Originally reviewed on Backcountry.com