One Hole, Hole Size 7 mm, Height 23.5 mm, Wide 15 mm, Thickness 9.5 mm Made of Polyoxymethylene (POM), also known as acetal, polyacetal, and polyformaldehyde, is an engineering thermoplastic used in precision parts that require high stiffness, low friction and excellent dimensional stability. Springs Made of Iron, Nickel-Free Plating