The water bottle mount is a convenient, simple to install way to carry up to four CO2 cartridges while on the road. *Mounts to water bottle cage brackets and holds up to four CO2 cartridges *Includes two 16 gram threaded CO2 cartridges *Built in Anti-Reverse Feature (Keeps cartridges secure durring rides) *Works with ALL threaded CO2 cartridges (except 45 gram) Will also take Big Air cartridges *Durable die cast construction. Item Specifications; Unit of Sale:Each; Weight:22.2g; CO2 Cartridge Type:Threaded;