get a dial back light. they ain't as accurate as a good basic Sears non dialback unit cause the delay is based on time and different harmonic balancers of different makes are different and they sure ain't calibrated at their factory for Mopar 7&1/4" dia balancers but they're good within 1 degree (mine was) & that's pretty good and supposedly MSD's play havoc w them but they are SO much fun to play with. Disregard the above information overload and get a fairly good one & have fun