PROTECTS YOU & YOUR CAR: Check the health status of DOT3, DOT4 car brake fluid, Brake Fluid Tester Pen can be used as a digital brake fluid tester suitable for determining brake fluid quality. It will be safe for your driving.EASY TO USE: Press the button , Insert the tester into reservoir for one second then the tester result will be correctly indicated by LEDs.Repress the button for power off.5 LED INDICATORS: Brake fluid detection pen is based on the change in conductivity to determine the moisture change brake fluid. It shows clearly the extent of moisture contained by the light-emitting diode.The LED indicators will show percentage of water in the brake fluid with 3 colors--Green,Yellow and Red.Red indicates the brake fluid needs immediate replacement, Green represents good condition, Yellow indicates the state is acceptable but soon replaced.USEFULL : Supports DOT3 DOT4 DOT5 brake fluid .PACKAGE CONTENTS: 1 PIECE Brake Fluid Liquid Tester with 5 LED Indicators.