Put the apex kit in both of my 642 well worth it . Just follow the YouTube vedio link they give you easy todo and made a big difference. Also I polished the sides of the rebound slide and areas of the frame that it rode in used very fine stone and 1500 grit paper . You are only polishing the sides and not the engagement surfaces so you should not have any problems .After the install and polish job used snap caps and 1000 pulls of trigger really improved the triger