APPLICATION: Great for road bikes and commuting bikes. CARBON SHAFT: Made of UD (unidirectional) carbon fiber which is twice as strong and tiff as woven carbon fibers, resulting in a light yet strong seat post for the weight weenies. Conveys pedalling power efficiently without any loss. LIGHTWEIGHT ALLOY CLAMP: Head clamp is made of 6066 aluminum alloy to reach the best balance of weight and cost. Adjustable design offers easy-to-set, secure, slip-free saddle positioning, allowing for quick and easy assembly and saddle angle adjustments. SPECIFICATIONS : Diameter: 27.2mm.