Toxic Waste Wheels in ULTRA HARD durometer made in SUPERTHANE urethane formula.  These provide serious speed on smooth surfaces. Best for concrete - parks, ramps and tracks 

• Formula: Superthane
• Durometer (Hardness):  VERY HARD 103a (=83b)
• Dimensions: 60mm with 25mm contact area
• Packaging: set of 4
• Made in the USA.