tapered bronze bristles of the Otis chamber brush scrubs the chamber, neck and shoulder. The tapered bronze bristles of the Otis chamber brush scrub the chamber, neck and shoulder. The steel bristles at the base scrub the star chamber of the locking lugs. The brass stem is cold welded to the core, and the tip is folded, not cut. The chamber brush has a standard 8-32 thread.table.productattributes, .productattributes td { border-bottom: 1px solid #ddd; border-collapse: collapse; padding: 2px; text-align: left; }