Heckler & Koch USP & HK45 LEM Trigger Conversion Kit Factory LEM conversion kit for USP and HK45 pistols HK LEM Trigger Kit for all USP and USP Compact pistols and all HK45 and HK45 Compact pistols. This universal factory Heckler & Koch LEM kit is complete with all of the parts required for the conversion. Comes with two hammer springs: The longer hammer spring is for all USP, USP Compact and full size HK45. The shorter hammer spring is only for the HK45 Compact. USP LEM and HK45 trigger pull weights: Use the trigger return spring that is already in your gun for light LEM trigger pull, approximately 4-5 lbs. Use the trigger return spring in the kit for the heavier LEM trigger pull, approximately 7 lbs.