GRAIN MOISTURE METER Lightweight, spring-operated penetrometer quickly measures the compressive soil strength Easy to use with easy-to-read results. Penetrometer is easy to use: push the indicating ring to the highest point touching the body and insert the piston until the calibration mark is level with the soil. The easy-to-read scale indicates strength from 0 to 4.5 tons per sq ft. The reading is maintained until manually reset. Penetrometer is constructed from anodized aluminum and measures 6-1/ 4 " L x 7/ 8 " dia. Use an allen wrench to loosen the stainless steel pin for cleaning