For DOT3 DOT4 Car Brake Fluid Liquid Oil Tester Pen O7K9 Indicator LED I8U4

1x Brake Fluid Tester (1.5V AAA battery not included). 0% LED: Water content in brake fluid. 1% LED: water content, H2O ≤ 1%, brake fluid above. 3% LED: water content, H2O ≤ 3%, brake fluid. 4% LED: water content, H2O≥ 4%, brake fluid must be.

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