65mm, 70mm, and 76mm longboard wheels are made with a secret gel soft urethane formula (78a) with multiple colors to choose from (this includes a set of 4 wheels). These wheels are perfect for cruising on the sidewalk or on the asphalt street because of the soft formula they are made from. They ride fast, smooth, and silent. Choosing your wheel size: Try to visualize what you’re going to be skating on and think about what type of ground is in your area. The 65mm are good for smooth surfaces such as regular sidewalks and smooth asphalt. The 70mm are better for rockier areas like rocky parking lots and rough asphalt. The 76mm are good for all types of heavy terrain because they absorb bigger rocks providing a smoother ride.