Pi Wheels are the result of a lifetime of skateboard product testing and desig.The urethane is the perfect blend of speed, grip, slide and durability. The Stone Ground Riding Surface eliminates break-in time…they’re ready to rip NOW! They feature a High Density Core for solid bearing seating and a crisp smooth roll. They are available in 56.5, 59.5, and 61.5 all have the best shape and are ideal for the modern all terrain skater, be it Park, Pool, Ramp, or Street. Truly the best wheels we have ever ridden.