Description:1.Size: Approx. 15cm/5.9"2.Power Supply: 1 x 1.5V "AAA" Battery (Battery not Included)3.Principle: according to conductivity changes to determine moisture change in brake fluid, with five different color LED indicatorIndicator Description:1.5 LEDs indicating the water % in the brake fluid:2.0% light indicates that the battery is OK, no replacement3.1% light indicates that moisture content of brake oil less than 1% , brake fluid has a good performance, and ease of use.4.2% light indicates that moisture content of brake oil less than 2%, brake fluid can be continued to use5.3% light indicates that moisture content of brake oil less than 3% , proposed to replace brake fluid.6.4% light indicates that moisture content of brake oil less than 4%, brake fluid should be replaced immediately.7.Note: Due to the difference between different monitors, the picture may not reflect the actual color of the item. Thanks for your understanding.Package Included:1 x Brake Fluid Test