Compatible with standard blowback-operated 9mm AR-15 systems, the MEAN Arms ExoMag Ejector AR-15 9mm 20-Round Magazine is designed to deliver faithful feeding performance with standard Mil-Spec and Commercial AR-15 lower receivers. Injection-molded polymer construction offers exceptional durability and natural corrosion resistance. The built-in ejector offers faithful service with standard blowback systems. Features a high-tensile steel spring and injection-molded polymer follower and comes equipped with a last round hold-open feature. No magwell adapter or tools required. Works with all 9mm ammunition, including hollow points.