Spitfire Hjalte F4 Lock-Ins Cinder Wheels Set White Black Flame 54mm/99d Burn through the streets with the Spitfire F4 Hjalte Cinder Lock-In 99a Wheels. Formula Four Performance Urethane lasts longer, withstands more abuse and performs superior to all other wheels. Designed to combine all the desired properties of a performance wheel without sacrificing any one attribute at the expense of another. Manufactured using a 100% pure urethane compound, Formula Four wheels out-performed and resisted flat spots longer with less wear than all other wheels. Higher rebound for faster speeds over rough and smooth surfaces with a hard durometer for a smoother, faster ride that won't mush out over time. Designed with an exclusive anti-stick compound that gives a fast, consistent, smooth slide all the way through. Wheels sold in a set of FOUR.