The ultimate BMX racing tire, the PowerBlock is designed to efficiently transfer pedal power and other rider inputs into lateral motion. In short, you'll roll faster with less wasted energy. The S-Spec version utilizes Tioga's thinnest sidewall for maximum suppleness and weight savings. Size for size, the PowerBlock S-Specs are the lightest BMX tires in the world. - Center Row--"Power Blocks" are precisely sized to balance traction with low rolling resistance. - Sidewall Texture--Specially designed texture pattern, strategically applied to the sidewall adds abrasion protection without sacrificing casing suppleness. - CYLEX 120 TPI superlight casing - UTC rubber compound - ISO diameter: 451mm