Weld-On Flange Kit for HKS Blow Off Valves is precision-machined from durable 6061 aluminum for a strong, lightweight connection. This kit includes an O-ring to ensure a leak-free seal and features a radiused weld fitting that allows the combining flange to simply screw on. This design makes it easy to switch to a different blow off valve in the future without replacing the weld bung. Each flange kit is sold individually.