With its durable construction and easy-to-read scales, the Deep Six is guaranteed to provide years of reliable performance. Designed to give temperature-corrected readings in warm water aquariums, readings can be read in ppt and specific gravity. The Deep Six is accurate to +/- 0.001 specific gravity. Every unit is pre-calibrated and individually tested for guaranteed accuracy. Easy to use with a new, revolutionary self-leveling feature. Wide-range specific gravity meter that takes its reading from 6 inches below the surface.