Signstek Digital Professional Automatical Switchover Non Contact Laser Photoelectric Photo Type Tachometer Auto zero adjustment, stores last, minimum, and maximum readings, values can be displayed by turn anytime. Measures the rotational speed with a visible red light beam from a powerful LED The housing has been carefully shaped to fit comfortably in either hand. High intensity class II laser measures from 2.5 - 99,999 RPM Extra large 5-digit LCD display, high accuracy of +/- 0.05%