SUNSTAR SPROCKETS DRIVE SPROCKET 520 17T 3D317Manufactured from case hardened chromoly steel for unparalleled strength and durability , Parkerizing surface treatment prohibits rust and corrosion, building resistance against those agents, resulting in a longer lasting, better appearance , Most race applications feature drilled weight reduction holes (depends on application tooth size) , Constructed of the same great quality and specifications that the Japanese OEMs have trusted and used since 1946