Accurately tunes the speed of your turntable. The Strobodisc's break-in groove creates the additional stylus drag necessary to accurately measure the realtime speed of your turntable and it can also be used to break in new cartridges. The Clearaudio 300Hz strobe light (sold separatly) allows you to more precisely measure the actual speed of your turntable.  Dual sided LP-33/45 speed at 60hz on one side and 300hz strobe on the reverse side.