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  • Castelli Undersaddle XL Bag
  • Castelli Undersaddle XL Bag Detail
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CastelliUndersaddle XL Bag

Item # CST00AI

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  • Black, One Size ($34.95)
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Item # CST00AI

Bring it all with you.

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.

Tech Specs
Tech Specs
1 pump
water resistant zipper
6 x 15 x 6 cm
Recommended Use
Manufacturer Warranty
30 days

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  • Familiarity: I've used it once or twice and have initial impressions

A saddle bag has a fairly simple task - carry the essentials to keep you rolling on a ride. This Castelli bag knocks it out of the park with sleek minimalist styling.


Not XL

  • Familiarity: I returned this product before using it

I never unpackaged this under-seat bag. The manufacturer calls it XL, but you know how Marketing works... to convince consumers of something other than the truth. This bag is NOT XL. I have another under-seat bag, one size, which is shorter, wider and taller - with more volume. The marketing tricked me; don't let it trick you if you are looking for a larger bag.

!!!Perfect Saddle Bag for Me!!!

  • Familiarity: I've put it through the wringer

This is exactly the saddle bag that I've been searching for. The attachments are straight forward with velcro on both. I don't have to worry about clips breaking. (I've always been a Castelli fan.) I like that it is a little bit smaller, but still fits everything I need. I've got my tube of last resort, chain breaker, multi-tool, spoke wrench, levers and mini pump all in their. It's secure for when I bomb descents and employ evasive maneuvers around these crazy Baltimore drivers. I would definitely buy it again!

Keep The Goods Protected

  • Familiarity: I've put it through the wringer

This bag not only features classic Castelli styling, but the bag holds all of your necessary goods while also protecting them from rain or wheel spray. This bag can fit multiple spare tubes, multitool, tire levers, an inflator, CO2 canisters, some patches, and even a minipump on the outside.

Not a purist

  • Familiarity: I've put it through the wringer

So I have the very cool Silca Seat Roll Primo for my road bike. Super stylish, perfect size! I NEEDED A MINIMALIST BAG FOR MY NEW SANTA CRUZ 5010. 1 tube, 1 multitool, 1 pump, 1 patch kit. Its all I want to carry. This Castello bag is perfect. It snugs up tight, doesn't sway, stays out of the way, and is water/mud proof. Apparently Castello makes great Mountain Bike accessories as well. Who knew!

Castelli bag

    Perfect for small personal items. It look great and light weight. It fits perfectly under seat on my F8

    Carry enough impotant things

    • Familiarity: I've used it several times

    With this bike I carry a tube,2 tyre lever and bike tool. And still have small free space.
    I just use it for 3 rides, each around 100-250 km ride. The shape is perfect for road saddle even with long oval shape f8 seatpost or common seatpost. This saddle bag not make discomfort when pedaling. I haven't test it on wet weather yet. I hope soon rain will fall and try is this bag good in bad weather. Tx

    Slick Seat Bag

    • Familiarity: I've put it through the wringer

    This is a really nice-looking seat bag, perfect size for a tube, multi-tool, and two CO2 cartridges. Plus it has a special pouch for a mini-pump. It reminds me of the Blackburn bags since it is made of a similar waterproof material. It replaced an Arundel bag, which I liked, but wore out pretty fast. This one has been holding up nicely. One little quip is that the mini-pump will easily come out of the pouch if you don't figure out a way to affix it. The fix I designed for it was two linked zip-ties that catch around either end, so that it won't slip out when I hit the next pot-hole. I had to reduce the rating on this item because after just one rain ride the velcro closures were ruined. I'm back to my tried and trusted Blackburn bag. Not as slick looking, but it withstands more punishment than this fancy bag.