This two piece caliber 5.56mm NATO .223 AR Rifle Brush Multi-Pack set fits standard American gun cleaning rod kits with 8-32 thread. This Bore brush and chamber brush set is designed for all AR rifle barrels in caliber .223 and 5.56mm. The AR-15 Rifle Phosphor bronze chamber brush with stainless steel bristles and Bore brush will keep your rifle's bore and chamber free of carbon residue build up and maximizes its accuracy and overall performance and work in all .223 Remington and 5.56mm AR-style rifles.