The Spitfire F4 99 Grant Taylor Undead Radial wheels are a specific model of skateboard wheels, featuring Grant Taylor's "Undead" pro graphic and Spitfire's high-performance Formula Four (F4) urethane in a 99a durometer for a balance of speed and control. They are a medium-profile, round-edged radial shape designed for versatile street and park skating, known for their durable, flatspot-resistant urethane and smooth, anti-stick sliding.