From The Manufacturer/Wikipedia/People Smarter Than Us:
The new Ultralight Carry was designed from the beginning to be the ultimate full-size carry pistol. The foundation is a fully machined aluminum frame for reduced weight. When combined with the carry cuts, ball endmill cuts, round butt frame, concealment beavertail grip safety and hammer, the Ultralight Carry is over 1/2 pound lighter than a comparable steel frame pistol.