Montana X-Treme Nylon Bristle AR Chamber Brush for Rifle (8/32 Thread) .223/5.56 SPECIFICATIONS BRAND: MONTANA X-TREME CA PROP 65: YES CLEANING CALIBERS & GAUGES: .223, 5.56MM CLEANING ITEM TYPE: BRUSHES MATERIAL: NYLON USAGE: RIFLE DESCRIPTION Montana X-Treme .223/5.56 AR Chamber Brushes are constructed on a brass core with very stiff heavy bristles that will not flatten and retain their memory like brass chamber brushes from other manufactures. Designed for a superior cleaning of lugs and chamber. Standard 8 x 32 thread.