1000 pieces 8mm - Catapult ammo Grade 1000 UHC Unhardened Carbon Balls (UHC) 5/16" Catapult Slingshot Ammunition (Actual Size: 7.938mm) These are carbon balls that are not subjected to the heat treatment process. These are widely used in non precision applications and more commonly as catapult ammunition. ***NOTE*** Catapult ammo balls are Grade 1000 unhardened chrome, which means sizes may vary slightly from the size shown on the listing. These are not for use as precision balls for engineering applications