The Extech 461825 Combination Photo Tachometer and Stroboscope can be used to measure tachometer RPM, as well as analyze stroboscopic speed and motion. Depending on the measuring mode, the distinctive display reverses the character direction. The tachometer memory retains the last, maximum, and minimum readings for recall. The strobe has three ranges for adjusting the course and fine flash rates. It comes with four AA batteries, reflective tape, and a carrying box.