Bones Wheels 81B SPF Pool Sharknado P5 Sidecut

About Skatepark Formula™ (SPF) Skatepark Formula™ (SPF) is a high-quality urethane specifically designed to prevent flatspotting on smooth surfaces while providing a higher rebound for faster response and rolling. Skatepark Formula™ has high abrasion resistance without compromising hardness and glide. Simply put: Skatepark Formula wheels grip better on smooth surfaces, making it almost impossible to get a flatspot, and they are the fastest and most durable wheels on the market. You won't find our Skatepark Formula with any other wheel provider, so grab a set and discover for yourself what SPF is all about.

About the Durometer B Scale The Shore Durometer A Scale is good, but it does not cover the entire hardness range of skate wheels and is very limited because the scale ranges from 1 to 100, and anything above 95A cannot be accurately measured. The Shore Durometer B Scale is perfect for skate wheels because it is very similar to the A Scale but shows 20 points less, allowing the useful scale to be extended by 20 points, covering the entire hardness range of skate wheels in one scale. It uses the same soft spring as the A Scale but the conical measuring needle of the D Scale. Since the spring is soft, the B Scale needle does not penetrate the surface of the wheel, providing the same reliable reading as the A Scale. The Shore Durometer D Scale is intended for hard rubbers and extremely hard urethanes, not for soft, springy urethanes used in skate wheels. It has a very stiff spring behind its sharp, conical needle and often penetrates the surface of the wheel being measured, resulting in a reading that is 5-10 points weaker than accurate. Therefore, the Shore D Scale should not be used for wheels suitable for skateboarding.