Adjustable size, compatible with various sizes of drink bottles. Features a rubber lock to prevent pet bottles from popping out. Easy to attach with Velcro, so it can be attached to camping chairs as well as bicycles. By removing the Velcro parts, it can also be attached to the MOLLE system or the shoulder straps of a backpack. (Not compatible with everything. A vertical loop is required.) It has been opened, but never used.