Double up on firepower for your home defense rifle with the MEAN Arms® ExoMag Ejector AR-15 9mm 40-Round Magazine. This magazine can be used with a standard AR lower and all you need is a complete 9mm upper receiver and bolt carrier group (BCG) to help facilitate quick and easy caliber changes from .223/5.56 to 9mm. The ExoMag features a last round bolt-hold open feature so your rifle functions like normal and a built-in ejector designed to perform in any intense conditions and it features lightweight polymer construction for durable strength. Plus, a polymer follower ensures smooth reliable feeding, and this magazine can shoot all 9mm ammo including hollow points. Backed by a lifetime warranty from MEAN Arms. Order some new mags today!