Wolff Gunsmith Kits, Blitzpaks and general purpose spring paks are generally intended for repairs where direct replacement springs are not available. A wide range of types and designs are included to solve many needs. These springs are produced with the same high quality material used in all Wolff springs and are intended to be custom fitted to a particular need. Because fitting of these springs is required, fitting and installation by a qualified Gunsmith is recommended.There are 15 different spring designs with 2 springs of each design supplied. Springs are designed to function in 1/16" to 1/8" and 1.5mm to 3.5mm inside diameters. Springs vary from 1/2" to 1-1/2" in overall length. Fitting of springs is required. This is a highly useful assortment to have on hand.