Featuring an impact-resistant polymer tube with a shock-resistant floor plate and compatible with any standard AR-15 lower receiver and converted uppers, the CMMG® MK4 / AR15 .22LR 25-Round Magazine offers smooth and consistent operation in virtually any target shooting or training application. The steel wire spring and hi-vis polymer follower deliver smooth, jam-free operation, while the removable floor plate allows for quick maintenance and cleaning when required. Better yet, this magazine features a last-round bolt hold-open functionality for improved safety and faster reloads. Backed by CMMG's legendary lifetime warranty.