Used to digitally test brake fluid quality. Designed for professional use in workshops. With 5 LEDs in total. One LED indicates battery quality. LED 1 and 2 indicate less than 1 to up to 2 percent water (acceptable) and LED 3 and 4 indicate 3 or 4 percent (unacceptable) percent of water in the brake fluid. Easy to operate. - Suitable for brake liquids: DOT3; DOT4 - Operating temperature: -20 ~ 40°С - Power supply: 1x 1.5V AAA battery - Includes battery - Probe size: 13.2 x 3.5mm - Dimensions: 150 x 23mm - Weight: 58 gram Note: Do not expose DOT 3/4 brake fluid to the atmosphere for any length of time since it is very hygroscopic (water absorbing). It is designed to be hygroscopic so when brake fluid is changed it is guaranteed that all water will also be removed from the brake system.