2.7" 8-rib pulley ring for 05-10 Mustang GT 4.6L 3V with Roush R2300 / P51 TVS Supercharger kit. This pulley is specifically designed for P51A single belt kits that have been converted to 8-rib with aftermarket parts. 15+psi Also works on cars with 6-rib belt system. This pulley bolts on to the Roush 6-bolt hub. Black annodized aluminum.