This product was designed to enhance the ergonomics of the 13 an 15 round extended magazines. The goal was not to so much add length, but to provide a positive stop for the last finger to keep the hand/grip secure. This grip consistency helps put more rounds on target. This unit replaces the magazine base plate on the M&P 9 SHIELD PLUS and 30 Super Carry. Also fits S&W EQUALIZER This extension does not alter the capacity of the magazine. It adds approximately 1/2" inch additional gripping surface and incorporates a texture pattern similar to the frame. FOR 13/15 round 9mm magazines and 16 round 30 SC ONLY. NOT FOR EZ FRAMES. NOT FOR ORIGINAL SHIELD "single stack" FRAMES.