Rebuilt engine valves can sometimes be mistaken for new Caterpillar engine valves. Some engine component rebuilders supply used Caterpillar engine valves that have had their stem diameters built up by a chrome plating process. Close visual inspection of a valve stem near the valve retainer grooves can show an indication of the chrome plating process. This area can have an uneven appearance where the chrome plating ends, see Illustration 1. Valve stems that are not chrome plated will have a smooth appearance as shown in Illustration 2.