Description: The main function of this brake fluid test pen is brake fluid quality determining. 5 LED lights display the percentage of moisture content in brake fluid, provides more accurate test result. Brake fluid tester is suitable for determining the quality of brake fluid and escorting your driving safety. The 3-color lighting is intuitive and convenient. Red indicates that the brake fluid needs to be replaced immediay. Green indicates that the brake fluid is in good condition. Yellow indicates that the brake fluid remains good, but it will change. The brake fluid tester determines the change in humidity of the brake fluid based on changes in conductivity. The humidity is clearly indicated by the light-emitting diodes. High levels of moisture will lower the boiling point and then affect the braking performance. Specifications: Color: black. Size:150mm. Material: plastic. Power supply: 1 AAA battery ( not included ). Package includes: 1pcs hello, guys, thank you for visiting my store. Dear buyer,Welcome to our store. Thank you for your attention, Thank you for your support!Welcome to buy from us!