Description: Replacement Wheels for Inline Skates, roller skates. Led inside the wheels with self-generating power. No battery needed.(When the wheel moves, it automatic light up) LED light beads, light up when the wheel moves, coil is made of pure copper, Cutting the magnetic induction line power generation, electrical energy into light energy, safety and environmental protection High quality and improved PU material, durable for outdoor uses. 80mm diameter wheels, universal use. LED Light Flash, very cool, your are the focus. Specification: Wheel Material: PU Magnetic Core Material: Copper Wheel Diameter: 80mm Wheel Inner Diameter: approx. 22mm Wheel Thickness: approx. 23mm Hardness: 85A Magnetic Core Diameter: approx. 18mm Magnetic Core Inner Diameter: approx. 9mm Package Includes: 2 Pieces Roller Skate Wheels (Bearings not included) 2 Pieces Magnetic Core Note: Color maybe slightly different due to different monitor. The above size is measured by hand, please allow slightly difference. Thanks!