This Taran Tactical Innovations M&P Shield base pad works on any full sized M&P Shield 9mm and 40 S&W handguns. This TTI base pad does add a little extra weight to the magazine which helps the empty mag drop free easier for faster reloads. This TTI M&P base pad just like all of the base pads is designed to give you the edge over your adversaries. The base pad is machined out of aircraft aluminum and is hard anodized to ensure durable long lasting color. *Adds 2 extra rounds for 9mm (Overall capacity: 10+1) Adds 1 extra round for .40 S&W (Overall capacity: 8+1)