Rollerbones Bonnie Thunders Signature Purple, 62mm 88a, Pack of 8 Wheels. Wheel Core: Aluminium Wheel Diameter: 62mm Wheel Hardness: 88a Wheel Formula: SAA Wheel Color: Purple Wheel Suggested Use: Derby/Jam/Speed Wheel Surface: Treaded Qty in Pack: Pack Of 8 wheels Rollerbones Manufacturing the best Roller Derby and Roller Skate Wheels for decades. Rollerbones was established in 1979 when a white MDI formula used by Powell Corp for skateboard wheels replaced a transparent TDI formula, the roller-skate industry standard. This change led to a shift in the industry as other companies followed. Rollerbones are poured in Santa Barbara, California. We are constantly evolving and improving our formulas to accommodate all disciplines of roller-skating. Quality products for the quality minded skater.