About: The amazing new X- Formula™ (XF) is another industry leading innovation from the BONES WHEELS factory. X-Formula rolls over rough terrain like softer wheels do, but slides much like a harder wheel will. Speed: X-Formula™ is extremely fast because it has a super high rebound. X-Formula rolls much smoother and faster on all terrains because it absorbs vibration and softens impacts much better than any other wheel in the market. Grip & Slide: The slide-ability comes from its unique blend of high performance materials. X-Formula will slide when you ask it to, and grip when you need it most. This is because X-Formula is specially formulated for any terrain. It has been developed over a ten year period to optimize performance and fine tuned to perfection. X-Formula is very unique product Durability: X- Formula™ is smooth, fast and durable. It has been developed using the highest quality, longest lasting materials. X-Formula is a great value and because it softens landings and absorbs vibration, it is also better on your body which can add longevity to your normal day of skating. These wheels will change your life!