Supertech High Performance Engine Valves, Springs, Valve Accessories, Pistons and Block Guards Valve Guide GDE-VW8V-7A Valve Guide 12,06mm x 40mm VW Intake & Exhaust Valve Guide from 8mm to 7mm stem Outer diameter: 12,06mm Length: 40mm Suggested Valve seals: VS-VW8E VS-VW8I The Valve Guides are precision-machined from high quality Manganese Bronze material. Valve Guides are designed to be used in combination with our low friction black nitrided valves to provide the best solution for both performance and durability. For exhaust valve guides designed to be used for high powered engines that need a better thermal transfer coefficient, a copper alloy guide is used. Copper has about a 3 times higher thermal transfer than Manganese Bronze.