We are excited and pleased to introduce the MEAN EndoMag™. This product is a magazine insert that converts your Gen 2 or Gen 3 5.56/.223 PMAG® housing into a 9mm magazine to use with a standard AR lower and 9mm upper of your choosing with a Glock or Colt variant 9mm BCG. Here is a list of features the Mean Arms 9mm Magazine Adapter are as follows: Quickly and easily change calibers from .223/5.56 to a caliber associated with the EndoMag in a Magpul 30-round 5.56×45 PMAGsⓇ (Gen 2 and 3) Functions as a magazine! No magwell adapter needed!