Chamber Brush Features 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. It is a standard 8 x 32 thread. Chamber Brush Specifications Brand: Montana X-Treme Cleaning Item Type: Brushes Material: Nylon Usage: Rifle