The AR-15/M4/M16 Speed Loader works with metal and polymer magazines. Magazines will securely lock into Speed Loader with the integrated magazine catch. Speed Loader works with GI 10 round stripper clips or you can load 10 loose rounds into the side tray that opens up for easy access. The side tray door is secured with a spring loaded latch. When the Speed Loader is loaded up with 10 rounds, insert the tethered T-handle push rod into the top of the loader and push the cartridges into the magazine. Load up another 10 or so cartridges until the magazine is at capacity.