The Kings unit uses a special replacement hammer pin with a dovetail end, which is received into a dovetail slot machined into the weak side lever. This avoids having the weak side lever held in position by only a tab which is conventionally held in compression under the right side stock (grip) panel. Personally, I like them, as the weak side lever is firmly attached to the gun and can't wobble or loosen. To me, at least, also makes the weak side lever feel more solid and "positive". Also, if you happen to shoot a hi-cap such as a Para, the King's unit negates the need to worry about how to secure the weak side lever. Not at all hard to install. HTH.