All USP's use a fiber-reinforced polymer frame stiffened by stainless steel inserts at areas subject to stress and friction. HK pioneered this use of polymer materials in the production of handguns more than 30 years ago with the development of the VP70Z and P9S pistols.The USP control lever, a combination safety and decocking lever, is frame mounted and quickly accessible, unlike the slide-mounted safeties common on many semi-automatic pistols. Using a modified Browning-type action with a special patented recoil reduction system, the USP recoil reduction system reduces recoil effects on pistol components and also lowers the recoil forces felt by the shooter. This same recoil reduction system has been tested and proven in the HK Mark 23 pistol developed for the U.S. Special Operations Command. The USP recoil reduction system is insensitive to ammunition types and requires no special adjustment or maintenance. It functions effectively in all USP models. Variant 1 is a double action/single action with "SAFE" position. Control lever (manual safety/decoking lever) on left side of frame.