From The Manufacturer/Wikipedia/People Smarter Than Us:
When you need a concealed carry pistol that offers excellent capacity and the ultimate in shootability, check out the XD-S® 4.0″ in 9mm. You’ll find yourself astonished at how easy it is to shoot this small pistol. You’ll be even more impressed with how well it carries. – See more at: http://www.springfield-armory.com/products/xd-s-4-9-mm/#sthash.PfvyTcnF.dpuf