The second and larger of our two seat packs in the Castelli race bag collection (images are not to scale) the Undersaddle XL is designed to carry a couple of of road tubes a multi tool and a C02 system (plus a external sleeve for a mini pump) with a little room to spare - Bt If your running trendy bigger tyres and hence bigger tubes you may need to select this over the mini to allow you two spares.
Held on my moulded magic Velcro (with a seat post stabiliser ) the bags simplicity is also its biggest asset. Water resistant fabric water resistant zips internal mesh pocket and well that's it. Just high quality minimalism.
Please note if you ride in heavy rain with no mudguards water will eventually get in to the bag so put everything in a plastic bag just in case.
Water and stain resistant materials
Water resistant zipper
Water resistant construction
Adjustable hook and loop attachment straps
External mini pump sleeve
Internal storage pocket
External Dimensions 6 x 6 x15cm