Slime Balls 66mm, 78a Friends of Planet 9 Glow in the Dark Light Ups with glow in the dark urethane and core. Slime Balls Light Ups wheels feature LED lights that light up when you roll, powered by the rotation of the special wheel spacer and wheel core. No batteries required. Light Ups come with removable / replaceable Bronson Speed Co. G2 bearings. Slimeballs OG Slime shape is a versatile, symmetrical center bearing cruiser wheel with soft, 78a urethane. 66mm x 47mm, 78A.