Three-Tone Audio Discrimination - sounds distinctive tones for different types of metals,to make target identification easier. Arm Support - lets you carry and operate your detector comfortably. Auto Tune - lets you tune your detector quickly for accuracy. Waterproof Search Coil - lets you use the detector to search under water. (The search coil is waterproof, but the detector's control housing is not waterproof.) Analog Meter -shows the probable type of metal being detected.