Where striker engages sear, on the original sear where it engages striker (irrelevant with GG kit), top of thing that pushes firing pin block up, surface on trigger bar that engages sear, rear area of trigger bar that rubs against FCU (front area around hole that trigger fits into I should do but haven't).
Shot the GG kit today and like it better than original trigger, I think the shorter reset (and total travel) really help, still would like the reset to be shorter.