Doug is correct. I too worked at Goodyear mid 70's. ET's had a plastic insert that went in the back of the rim to select bolt pattern and washers on front. It was a 1 piece circle. Cheap design. We had a drawer all them because they would wear. I have a set for chevy 4.75 bolt pattern from a set of Ansen sprint 2. They used an egg shaped metal insert in the back of rim and a center or offset washer on the front. 1 was center for 4.75 then the other insert could be installed at 4.5 or 5.