The 0940 is a GLOCK magazine compatible AR-15 matched lower and upper receiver set that accepts 9mm, .40S&W and .357 Sig GLOCK magazines. It features last round bolt hold open Last round bolt hold open on an empty magazine Flared magwell for faster reloads Lower receiver accepts 9mm, .40 S&W and .357 SIG GLOCK(R) magazines Integrated, oversized trigger guard 7075-T6 billet aluminum lower receiver with a matte black hard-coat anodized finish 7075-T6 billet aluminum slick side upper receiver with appropriately sized ejection port and no forward assist or dust cover Threaded bolt catch screw For use with a 9mm bolt carrier assembly and a standard AR-15 hammer Upper weight: 6.5 oz Lower weight: 10 oz Patent pending Accepts most all aftermarket Glock(R) 9mm double stack magazines. We recommend using factory Glock(R) magazines