This is a cool little tachometer for a four-cylinder engine, the needle seems to move freely. The outside diameter of the chrome ring is 3 inch on the body of the gauge and the chrome ring for the tachometer is 2 inch to the outside ring. Not sure if this works or not but most likely it does yet it is being sold as is. It could use a cleaning and if you noticed, there’s a small crack where the nut tightens up to the back of the gauge, but should not affect anything.