I's the flat piece of steel hanging down at the front of the action.
I'm pretty sure the aftermarket recoil lugs you've seen need to be fitted by a gunsmith.
Just wait till you need a new barrel.
I just got a Rem 700 Tac aac-sd
Well I see someone bought into the marketing hype.
Well I see someone bought into the marketing hype.
Original recoil lug is fine. You don't need an aftermarket one.
BTW, did you get a Sound Suppressor with the rifle?
AFAIK that rifle was specifically designed for subsonic suppressed shooting which is something you are unlikely to do. IIRC it has quite a fast twist rate.