Like all Wolff springs, these for the 1911 Auto in .45, .38 ­Super or 9mm are the finest, most reliable, longest lasting ones available. The springs of choice for most of the nation's top builders. Except where noted, all recoil springs are supplied with an extra power firing pin spring that keeps the firing pin stop in place and prevents firing pin “float”; an addition recommended by pistolsmith Bill Wilson. TYPE D - Extra Power For Hardball and Heavier Loads in Commander - Provides same benefits as Type C springs, but for the shorter Commander which comes standard with an 18 lb. spring. Includes extra power firing pin spring.