The Aero Precision EPC-9 receiver set is the perfect foundation for your next AR9 build. Precision machined from 2 custom 7075-T6 Aluminum forgings and featuring a last round bolt hold open. Compatible with standard frame Glock magazines, the EPC-9 receiver set is compatible with 9×19 and .40 S&W when using the appropriate bolt carrier and barrel. EPC-9 Lower Receiver Features: Threaded bolt catch pin for easy installation. Integrated enlarged trigger guard to remove any risk of breaking off trigger guard tabs, and provide an overall more rugged platform to build on. Threaded takedown pin detent recess to allow for the installation of a detent and spring with a Mfg: Aero Precision