I bought the best one Innova has, the 5568. It is awesome, it has many helpful functions, but they are really easy to use. Acts like a mini engine analyzer. Reads Tach, V, dwell, it works with multi-fire ignition boxes like MSD, and the best of course is the digital advance/retard knob. It has a shock proof casing, and comes in a nice sturdy carrying case. It's fancy but not over the top with options the average mechanic wont use. Im really impressed with mine