A Stroboscope Disc and Quartz Strobe light. The AT6181DL kit includes a stroboscope disc along with a quartz strobe light, giving you everything you need to precisely check your turntable's rotation speed. The light’s yellow LED provides a clear, accurate reading of the stroboscope’s high-contrast markings for 33-1/3, 45 and 78 RPM speeds. Stroboscope disc also includes an overhang guide.