Spitfire Formula Four 99D Conical Full 54mm — Precision-poured urethane for technical street skating. The Formula Four 99D Conical Full 54mm delivers Spitfire's legendary Formula Four urethane in a 99D hardness — the choice for slick, fast terrain and technical ledge work. The conical full shape provides a wider riding surface for flat-ground stability while shedding weight at the inner edge for a more responsive feel. Poured in-house at Spitfire's San Francisco facility, these wheels hold their shape and resist flatspotting through repeated heavy use. Formula Four Urethane: Spitfire's proprietary compound — no flatspotting, no chunking, consistent speed on smooth surfaces Hardness: 99D — firm and fast, ideal for skate parks, marble ledges, and sealed concrete Diameter: 54mm — versatile mid-size suited to street and park setups Shape: Conical Full — broad contact patch for flat-ground control, relieved inner edge for grip transitions Made in the USA at Spitfire's SF facility At 99D, these roll fast and stay true session after session — whether you're grinding granite curbs or lacing tricks on a polished skatepark floor. The 54mm diameter keeps your setup agile without sacrificing roll speed across gaps and flatground. Setup Guide: Sold as a set of 4. Compatible with standard 8mm axle hardware. Pair with bearings sold separately. Best suited for riders on medium-to-stiff decks who prioritize speed and slide consistency. Care: Rinse with water after skating in wet or gritty conditions. Rotate wheels periodically for even wear.
