On the very front of the reciever is a reduced diam. section the same thickness ( front to back ) as the ring. The ring fits on there. The small part of the ring is underneath , the large part up to take the handguard. You will see a little cut out in the A3 stock for this ring to fit into so that will tell you if it's all the way on. It does fit onto the smaller reciever OD and butts up against the larger OD.
Chris