A simple tool for testing the percentage of water in brake fluid - essential for regular safety checks on your brakes. Colour coded LEDs show the level of water. Suitable for Dot 3, Dot 4, Dot 5.1. Not suitable for silicone based Dot 5. Requires 1 x AAA battery (included). CE & UKCA compliant. The tester indicates the water level with the following LEDS: Green - Battery OK, No water found. Yellow - Less than 1% water, No action necessary. Yellow/Yellow - 2% Water found, Check regularly. Yellow/Yellow/Red - 3% Water found, Change brake fluid. Yellow/Yellow/Red/Red - 4% Water found, Brake Fluid should be replaced.