Atom Super G Quad Indoor Roller Skate Wheels - Perfect for Roller Derby Skates - Your Choice of 88A Blue 59mm Wheels or 91A Red 62mm Wheels - MIND BOGGLING is how we"d explain this wheel. Super G features a full urethane front supported with a large back mini-core. We"ve never used this mini core before but it proved its worth in testing. Looking for something that has more grip than a Stinger but not as soft as a Poison?, this is your wheel! - Perfect for: Wood, Sport Court, Polished Concrete