Heavy duty jaws lock on to three sides of a hex fastener and will not slip or mar. Designed to replace up to 16 wrench sizes. Includes a built-in wire cutter. Turn screw to adjust pressure and fit work. Stays adjusted for repetitive use. Constructed of high-grade heat-treated alloy steel for maximum toughness and durability. Guarded release trigger quickly unlocks and protects from accidental release.