Extech RPM40 Pocket Contact and Laser Photo Tachometer Item is a Class II laser product, 1mW power output. Large 5-digit LCD where characters on display reverse direction depending on measurement mode you are in Microprocessor based with quartz crystal oscillator to maintain high accuracy Provides wide RPM (photo and contact) and Linear Surface Speed/Length (contact) measurements Laser guided for greater distance non-contact measurements up to 4.9ft (1.5m) Memory stores Max/Min/Last readings