The Bolt Action PRO .223-.308 USB Chamber Chiller is designed to fit short, long and magnum bolt action rifles as well as other semi-automatic rifles and bolt action rifles with a minimum ejection port opening of 71mm length by 12.30mm height (2.80 inches length by 0.49 inches height). It is ideal for rifle cartridges with a rim diameter of 9.60-12.10mm. The Bolt Action PRO .223-.308 USB Chamber Chiller uses a 60mm turbo fan and an external USB battery pack. The PRO model utilizes a higher performance fan and comes with a removable filter and rechargeable USB battery pack. Please Note: *** The Chamber Chiller nozzle should only touch the outside edge of your chamber. The nozzle should not be inserted all of the way into the chamber. *** Rechargeable USB battery pack included. Fits: Cartridges with rim diameters between (9.60-12.10mm)