Holosun Technologies 509 Adapter, Black, Fits HS507C Footprint 509PLT-507C The Holosun 509 Adapter for 507C footprint is a rugged and reliable mount, perfect for use with law enforcement, the military, and the everyday shooter. CNC machined with 6061 aircraft aluminum with a Type III Hard Anodized Finish, this mount is designed to withstand even the hardest-hitting recoil as well as rough use and abuse in virtually any tactical environment.