These cartridges.....co2 cartridges - Walmart.com used in this pump/CO2 combo.....http://www.nashbar.com/bikes/Product_10053_10052_172872_-1__ gets my 23mm tires up to 125psi every time. I used to have a trigger lock CO2 dispenser. Could use a bit, lock the lever, come back within a couple of hours to finish the cartridge off.