The Foxtrot Mike Products FM-9 Heavy P.C.C.Buffer is the perfect weight to ensure reliable feeding of any blow-back operated P.C.C. 3.7 inch overall length, requires no spacer and helps prevent bolt catch breakage. Smoother function, less felt recoil, and reduced rate of fire from your AR pistol. Compatible with all blow-back 9mm upper receivers; Salt bath Nitride Melonite/QPQ finish gives lubricity and wear-resistance; Heavy 6.5 oz. (pistol) weight