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. Specifications Stroboscope Disc Speeds: 33-1/3 RPM, 45 RPM, 78 RPM Dimensions: 104 mm (4.09") diameter Weight: 35 g (1.23 oz) Strobe Light Frequency: 33-1/3 RPM, 45 RPM: 120 Hz 78 RPM: 234 Hz Battery: AAA (alkaline or nickel-hydrogen) × 2, sold separately Battery life: Approx. 8 hours (continuous use) Dimensions: 32 mm (1.26") W × 19 mm (0.75") D × 115 mm (4.53") H Weight: 35 g (1.23 oz), without batteries