Features :Surface: Wider contact surface with the ground, rolls all kinds of road surfaces, over the obstacle ability.Noiseless: High-speed rotating bearing, noiseless, smooth rotation speed and more durable. Smooth sliding: Our magnetic core has a protective cover, which is not flimsy but also allows the wheels to flash more and slide more smoothly. Comfortable: Polyurethane polymer material, non-slip, wear-resistant, good compression resistance, four-wheel polyurethane shock absorption, glide more comfortable. Application: Suitable for double row roller skates and four wheel skateboards. Material: Polyurethane. Color: 1 (red), 2 (blue), 3 (pink), 4 (white), 5 (red blue green), 6 (pink blue green).VDimensions (diameter x thickness): approximately 58 x 32 mm. Spring: 80% Contents: 16 ball bearings.8 x magnetic core.8 light wheels.1 spanner.