Dark web websites: How to access them safely and where to find dark web Draper 12V Digital Brake Fluid Tester with Printer. This brake fluid tester quickly and efficiently checks the water content of brake fluid. It features an LCD display with an analogue bar graph for easy reading. The flexible test probe is made of durable stainless steel. The device allows for rapid detection and includes a sound alarm. It has a built in printer that provides printed test results for evidence of safety checks and servicing. The tester is powered by a 12V car battery and comes with positive and negative lead with clamps and a roll of printer paper.