Features: This speed test disk is specially designed to detect the rotation speed of for 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 for LP vinyl record players. Specifications: Material:Acrylic Color:White Diameter:Approx.80mm/3.15in Thickness:Approx.7.5mm/0.3in Package Includes: 1x for LP Vinyl Phono Speed Test Disk note: Please allow 1-2cm errors due to manual measurement,pls make sure that you do not mind before you order. Due to the difference between different monitors, the picture may not reflect the actual color of the item.