This easy to mount and easy to use bottle cage affixes to 7/8" tubing, the size of most handlebars and all of our SeatSide Mount Mounting Bars. We don't make this item; it's a good quality system that we were able to find after a fair bit of searching and testing. The clamp size is natively 7/8" (22.2mm), so it doesn't need shims to clamp to handlebar sized things and to our Seatside Mounts and Handlebar Accessory Mounts. Turns out a Seatside Mount can be a handy place to stash another water bottle!