EFORCAR Brake Fluid Tester, Automotive Shop Tools Diagnostic Testing Tool Auto Brakes Calibrated with 5 LED Indicator Brake Fluid Oil Detection Mini Pen Liquid Moisture Water Tester Tool For DOT3 DOT4 EASY TO USE: Insert the tester into reservoir for a second,then the results will be indicated correctly by LEDs LED LIGHTS: 5 LED lights show percentage of water in the brake fluid. Change brake fluid if percentage is more than 3% TEST FLUID TYPE: DOT3 DOT4 POWER SUPPLY: 1.5V "AAA" x 1 (not included) NOTE: Clean filler cap on car's brake fluid reservoir before removing