AccuTech™ Digital Tachometer - 10KState of the art electronics give you accuracy to within 10 RPM Ultra light weight only about 1 1 2 ounces Fast response Easy recall High RPM warning light helps prevent accidental over revving of expensive motors Tach function is self powered (battery lasts 300+ hours) Optional connect to car for back light Includes mounting bracket also helps protect tach from damage 0 10,000 RPM 3 1 2 x 1 1 2 Uses CR2032 battery Note: This tach is reasonably water