Features: This speed test disk is specially designed to detect the rotation speed of LP vinyl record. 45 rpm (inner rings) and 33 rpm (outer rings), two speed gear are suitable for most phonographs on market; Made of acrylic material, it is durable, reliable, high quality and high precision. It can test whether the speed of the turntables is accurate, debugs the overshoot of the cartridge. It is an indispensable debugging tool for playing LP vinyl record players. Specifications: Material:Acrylic Color:White Diameter:Approx.80mm/3.15in Thickness:Approx.7.5mm/0.3in Package Contents: 1x LP Vinyl Phono Speed Test Disk Only the above package content, other products are not included. Note: Light reflection and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.