Genuine Innovations 25g Threaded CO2 Cartridge 2-Pack 25g CO2 capacity with threaded end 25g size is specifically designed for larger volume 29er and fat bike tires One 25g cartridge inflates 29x2.1 tire to 46 psi or 27.5x2.4 tire to 40 psi Includes two 25g threaded CO2 cartridges