Spitfire F4 Tablets Skate Wheels Set Natural Blue 51mm/99d Spitfire Formula Four 101D Tablet shape- An original SPITFIRE shape. Straight Cut Profile. Thin Riding surface. Lightweight, Quick and Responsive. In Spitfire's amazing Formula Four urethane. Take these wheels to the park or pool and shred the 'crete to deathTested by Spitfire Team riders, Formula Four Performance Urethane lasted longer, withstood more abuse and performed superior to all other wheels.