Ultimate Arms Gear .223/5.56mm Caliber AR15 AR-15 M4 M-4 M16 M-16 Rifle Chamber Brush Bronze Bristles Stainless Steel Tufts Military Style 8-32 Thread to fit Standard Rods 8-32 Thread to Fit Standard Rods. Tapered Bronze Bristles Scrub The Chamber, Neck and Shoulder. Steel Bristles At The Base Scrub The Star Chamber of The Locking Lugs. Brass Stem Is Cold Welded To The Core, and The Tip Is Folded, Not Cut. Length: 3.7". Weight: 0.2 oz.