Designed for M-16 AR-15 and similar rifles. Both the bore and chamber brushes have the core wire looped through a brass coupling threaded #8-36. The bore brush will clean any .22 .223 and 5.56mm. The chamber brush is configured with two brush diameters; the first stage of phosphor bronze cleans the chamber area while the second stage of stainless steel cleans the bolt lock up area. Please note that the #8-36 coupling is not a standard thread size and will not fit most commercial cleaning rods. However these will fit most Kleen-Bore multi-section rifle rods found in the Classic Rifle Kits and the All Caliber (S-170) Rod Set.