This is the frame mounted decocker version. I have no real problem with these other than they are a mother to put back together. I would not recommend you remove the "c" clip from the right side of the frame. It gets lost easily and the gun won't work w/out it. If you really know how to take it down good luck. I would never take one to a gunsmith who had not been to a S&W school. even then He likely does not understand the mechanism.