The OG Classic takes Spitfire's iconic Classic shape and widens it out for a vintage-inspired profile with more contact patch and stability underfoot. It's molded in Formula Four, the proprietary urethane Spitfire introduced in 2013 for flatspot resistance and consistent grip — part of the legacy Jim Thiebaud started when he founded Spitfire in San Francisco in 1987. This set comes at 55mm, 99a durometer.