Formula Four Pedro Delfino Turbo Pro Radial 97 professional skateboard wheels. The new reformulated 97s combine the soft duro compound of 93s with the slide of Formula Four 99s. Designed for every spot, holds speed through even the roughesst terrain. Natural 97 duro urethane. Radial shape. Full riding surface round edge design for control, speed and responsive slide. Diameter: 57mm. Width: 35.5mm. Riding surface: 22mm.