Supertech High Performance Engine Valves, Springs, Valve Accessories, Pistons and Block Guards Valve Guide GDE-HB55-I Valve Guide Honda 12,07mm x 41,7mm Valve guide intake, Honda B/H series, 5,5mm stem, Manganese Bronze Outer diameter: 12,07mm Length: 41,7mm Suggested valve seal: VS-H5.5-I 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.