Powerbuilt Universal Brake Fluid Tester Pen for DOT3, DOT4, DOT5.1 – 647766 (Black). You can quickly and accurately assess the condition of theDOT3, DOT4 or DOT5.1 brake fluid in your vehicle with this simple, effective brake fluid tester pen. 5 LED indicator lights let you know how much water content is in your brake fluid so you can determine when it’s time to change the fluid. This pocket-sized tester comes complete with a AAA battery and cap to protect the testing prongs from dirt or damage between uses. -Simple, accurate tester for DOT4 brake fluid -5 LEDs offer visual indicator for water content in brake fluid -Easy and economical way to monitor condition of the braking systems in all your vehicles -Great for shops and DIY mechanics -Includes battery and protective cap &#9888 WARNING: Attention California residents: This product may contain &nbsplead, a chemical known to the State of California to cause cancer and birth defects or other reproductive harm.