The Holosun 407/507K Adapter for FN 509 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.Features :Compatible with FN 509 Optic Cut Slides6061 aircraft aluminum constructionCorrosion-resistant anodized finish