Factory replacement parts are manufactured to the exact same specifications and tolerances and use the same manufacturing materials as the original parts. Some parts may require installation by a qualified gunsmith. Kit consists of 20 general purpose light-duty coil springs manufactured to English standards. There are 10 different designs with 2 springs of each design supplied. Springs are designed to function in 3/32" to 1/4" inside diameter openings and vary in length from 2 to 4 inches overall. This is a highly versatile selection of light-duty coil springs.