The all new Envy Hollow Core Wheels have been redesigned to have a thicker urethane and more of a round shape so that you have more surface area for the wheel to make contact with on the ground. Hollow Core Wheels have a very unique design machined into the core. These scooter wheels are super lightweight and durable. Made from hollow core technology to produce some of the lightest scooter wheels on the planet, Hollow Core Wheels are available in 110mm or 120mm. 86A urethane provides more grip than a harder urethane. ABEC 9 bearings ARE included. Hollow Core Wheels are sold in PAIRS.