Stroboscope Disc, Professional Vinyl Turntables Calibration Disc for Vinyl Record Player Specification: Item Type:Turntable Stroboscope Disc Material: ABS Color: Black and White Function: One side is the speed measurement function, the other side is the head angle calibration function Speed: 33/45/78 RPM?50/60Hz Scope of Application: Suitable for Vinyl Record Players Package List: 1 x Turntable Strobe Note: 1. The speedometer must be tested under a 50Hz strobe light. 2. It cannot be used under DC powered LED lights.