NavPlus Brake Fluid Tester Automotive Shop Tools Diagnostic Testing Tool Auto Brakes Calibrated for DOT 4 Brake Fluids (Battery Included) Quick and easy way to test for moisture content in the brake fluid; results appear in seconds! LED light indicators show percentage of water in the brake fluid. Calibrated for cars using DOT 4 brake fluid only (found in most cars produced since 2006). Takes 1 x AAA/1.5V battery (included). Only takes seconds to know the results.