Boren is right, it's Laylax Zero Trigger
and PDI V trigger
. Small change but it can be a big deal depending on if you decide to go with and then the upgrade path since IIRC Laylax and PDI cylinder systems don't like each other or something. V Trigger is a harder trigger pull but more robust while the Zero trigger is light as a feather but not as robust (but should be able to survive sub 500 FPS no problem).