All USPs 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. The USP recoil reduction system is insensitive to ammunition types and requires no special adjustment or maintenance. The modular design of the USP's internal components allows the control lever function to be switched from the left to the right side of the pistol for left-handed shooters. The USP can also be converted from one type of trigger firing mode to another. Variant 7 is a double action without control lever (no manual safety/decocking lever).