Can someone tell me what each of these parts do?
What kind of improvements do they offer?
SEAR:*
Striker Block:*
DCAEK:*
Polish/Trigger Job w/Apex Components:*
Apex Tactical FSS:*
RAM:*
Randy describes his parts on the APEX website. Plus, there have been several threads here. Search for APEX. Here is a link to one of them: https://www.m4carbine.net/showthread.php?t=81495. You could also search Randy Lee.