Finest quality coil springs, controlled-tension wound for smooth operation without binding under compression. X"XOver-PinX"X springs are designed to function over gun pins and plungers; X"XIn-HoleX"X springs are made to fit inside restricted areas. X"XIN-HOLEX"X MASTER KIT – Combines Kit #1 ID-12 and Kit #2 ID-12 for a total of 12 springs for in-hole use. Mfg: Brownells SPECS: High tensile spring wire. 12" (30.5cm) long.