This is a mount made by the manufacturer of the ACOG. this adapter will let you mount your ACOG to a flat top upper or any picatinny rail. Uses the large thumb screws that are common on the removable carry handle.
I mounted my ACOG but it has remained in the safe since mounting.....no rounds fired since I mounted it. It is in New/excellent condition.
Retailed for over $70. Asking $45 shipped.