I had an old post with all these part numbers, but can't find it. From CGW, you will need a trigger, either #5SAO(oem style) or #6SAO(flat). Both of these triggers have pre and overtravel screws. You'll also need a floating trigger pin(TR-PIN) and a reduced power trigger return spring(RP-TRS) if you want. Some people like the oem return spring for a crisper reset. On the guns I've done, the rp-trs is worth about a 1/2lb reduction in pull weight. Either way, buy an extra return spring. You can use the OEM hammer with the disconnector removed, but a Cajun race hammer or CZC Comp hammer will greatly improve pull weight and break. You will also have to file the safety leg on your sear or buy a CGW adjustable sear(AS-B)to use an aftermarket hammer. If you go with the adjustable sear, you'll need this spacer as well( S-Spacer). Lastly you'll need a hammer pin(HPIN). I would suggest buying a starter punch from CGW if you don't have one(to remove the OEM trigger pin). With an OEM Tac Sport hammer(works if your gun came with a wide hammer), OEM mainspring, oem sear, and rptrs, my SAO pre-B trigger pulls at 2.5 lbs. You can go lighter by bending the trigger return spring, but the reset won't be as positive. I think that's everything, somebody will chime in if I forgot something.