88g (3 ounce) Co2 canisters for use with Co2 airguns designed specifically for their use (88g/AirSource-specified products). Fits (among other things): Hammerli CR-20 Hammerli 850 AirMagnum Crosman 1077AS Crosman 2250XT Crosman Nightstalker IZH (Baikal) MP-661K