We offer this super cool plate window made of Lexan, which allows you to see down into the lifter valley area of the engine, (even while it is running!) and get a good idea of what is going on with your valvetrain. Use this with either our "B" and/or "RB" CNC aluminum valley plates. This part number includes the center Lexan plate only, the actual aluminum CNC valley pans are a separate part number.