From The Manufacturer/Wikipedia/People Smarter Than Us:
Smith & Wesson’s new M&P SHIELD™ is a slim, concealable, lightweight, striker-fired polymer pistol. Available in 9mm and .40 S&W, the new M&P SHIELD features a slim design combined with the proven and trusted features found in the M&P Pistol Series. From the pistol’s easily concealed one-inch profile to its optimized 18-degree grip angle, the M&P SHIELD offers professional-grade features that provide consumers with simple operation and reliable performance.