Moment Of Inertia Disc On Magnet, 17.5 Cm Dia. Plastic Disc Mounted On Ball Bearing And Magnetic Base, Plastic Disc Dia. 17.5 Cm Mounted On Ball Bearing And Magnetic Base Perforated With Hole At 1 Cm Interval On 12 Axes At 30 deg. Supplied With 6 Moveable Pins.