The unique design of the Deep Six Hydrometer allows hobbyists to take water samples at six inches in depth without submerging their hands in the water, thus avoiding the possibility of contamination. The world s first wide-range specific gravity meter that takes its reading from 6 inches below the surface. Every unit is pre-calibrated and individually tested for guaranteed accuracy. Easy to use with a new, revolutionary self-leveling feature. Durable Construction For Long Life.