Polythene wheels provide an aditional style that can be used where weight reduction is important or a more traditional retro-engineered look is needed. (They also look great as flywheels). The wheels are 75mm (2.95") in diameter, 5.5mm (0.21") in thickness , with a center hole to push-fit onto a 3mm shaft. The center can be drilled out to accommodate other diameters. 2/pkg.