Good workmanship, symmetrical tight fit on square bore manifold. Used with the Holley 4160 carburetor to maintain proper throttle clearance on the stock Mopar 67 440HP manifold. I also vouch that it helps reduce heat transfer and minimize vapor lock. The 4-hole spacer ring is said to have helped reduce engine power at low rpm and eliminate stumble at idle - and it did just that for my application.