BC valves are one piece design with a friction welded Stellite tip for the best possible performance. Every valve is made from premium grade, heat resistant stainless steel material to insure reliability with high boost and/or high rpm applications. The undercut stem above the head area not only reduces overall weight for extended rpm potential, but also significantly improves air/fuel flow in and out of the combustion chamber. Every valve is fully machined and features a swirl polished finish under the head. 31.0mm Exhaust (+1mm head diameter)