Whites went back to Eric Foster's advice and original design for the TDI Pro for OZ. The present circuitry for the Pro gives increased sensitivity to small gold (and nickles) and Eric also came up with a better coil match with the Pro for OZ. It now has a greater increase to small gold than the standard TDI and when teamed up with a RB 5X10 coil, one can pick up .1 gram pickers at a depth of 2 to 3 inches. The Pro is also very good at the beach in salt water or wet sand. I chest mount my Pro also, thus, I am able to work the beaches at ankle depth in water at low tide. I just hope that the reliability is now better than the previous TDI's that I have owned.