JL Billet M-Lok Arca Mount 3in Black. Arca rails are compatible with a wider range of accessories including Arca-Swiss style tripods bipods and mounts. They are also more secure thanks to the Arca-Swiss quick-release system. This system allows you to quickly and easily attach and detach accessories without having to re-zero your scope. Specifications for JL Billet M-Lok Arca Mount: Manufacturer: JL Billet Color: Black Features of JL Billet M-Lok Arca Mount Made with Aircraft grade aluminum. Allows for quick detach and easily re-zero your optic Package Contents: JL Billet M-Lok Arca Mount JL Billet ARCA-3": M-Lok Arca Mount 3in Black