1/2" ID Hi Performance Silicone Caps for Coolant, Water, Air, Vacuum, Emission, Water Ports, Turbos, and more. Reinforced 3-Ply Silicone Bypass Cap with black stainless clamp, Throttle Body, Water Ports, Heater Cores Packed 1 clamp + 1 black SS clamp per package High Performance 1/2" ID (13mm) Reinforced Silicone Coolant Cap - High Temp â Black/Green Enhance your vehicle's cooling system with these high-performance high temperature reinforced black silicone caps.