The specialized co2 replacement 25gm cartridge 25g replacement cartridges for the cpro2 trigger and airtool combo2 pump specialized co2 replacement 25gm cartridge features threaded screw type for reliable and safe filling 25g has enough pressure to fill a 29 x 23 mountain bike tyre 40psi max 16g has enough pressure to fill typical road tyres to 100psi compatible with screw type refills and specialized cpro2