Loosen frozen screws or securely tighten those that want to work loose (like scope base screws). Gives rotary impact power that hand tightening can’t, and won’t twist screw heads off. Mfg: Lisle Corporation SPECS: Driver, 1 1/4" (3.2cm) diameter x 4 3/4" (12.0cm). Steel. 3/8" (9.5mm) sq. drive male end. Bit Holder, 3/8" (9.5mm) sq. drive (female) socket adapts 1/4" (8.0mm) hex bits (MAGNA-TIP) to 3/8" (9.5mm) sq. drive (as on Impact Driver). Set contains: