Function Commonly used to keep valves from accidentally falling into cylinders when replacing valve springs or valve stem seals. Material Made of high quality copper and rubber with great durability and sturdiness. Anti-rust. Anti-corrosion. High pressure resistance. Features This valve holder adopts two-step fitting for both 14 mm and 18 mm spark plug holes. The heavy duty 12″ flexible hose can easily reach the spark plug hole and solve the problem of air supply. Easy to Install No need to take the cylinder head off. Just thread one end into the spark plug tube and attach the other end to an air compressor. Satisfaction Guarantee .