This unit replaces the magazine base plate on the M&P 9 SHIELD PLUS and S&W EQUALIZER. This extension does not alter the capacity of the magazine. It adds approximately 3/4" inch additional gripping surface and incorporates a texture pattern similar to the frame. FOR 10 round 9mm magazines and 13 round 30SC ONLY. NOT FOR 13 ROUND 9mm MAGAZINES NOT FOR EZ FRAMES. NOT FOR ORIGINAL SHIELD "single stack" FRAMES.