Lezyne 25G Threaded CO2 Cartridge - 5-Pack Refill Standard Co2 Cartridge 5 pack of cartridges in either 16G or 25G 16G:Inflates one race strap (27 '') up to 120 psi / 8.3 bar or inflates one mountain bike tire (26 '') at 30 psi / 2.1 bar 25G:Inflates one mountain bike tire (26 '') at 40 psi / 2.8 bar