The Box Components Box One QR Seat Clamps are cold-forged, and CNC machined from 6061-T6 aluminium alloy. A long and sturdy quick-release lever makes adjusting your seat height quick and easy. Weighing just 28 grams in the 31.8 size, it’s as lightweight as it is tough.The head of the quick-release lever and the face of the clamp are given a proprietary zero friction” surface treatment that ensures smooth lever action for the life of the clamp without the need for a bush.Who's this item for: Riders looking for a replacement seat clamp with an easy and smooth actionMaterials: Anodised drop forged and machined 6061-T6 Aluminum with Titanium hardwareClamp Style: This is a quick-release seat post clamp for quick height adjustments.Diameter: This is a 31.8mm clamp suitable for seat tubes between 31.8 and 31.5mm diameter, most likely a 30.9mm seatpost.Note - The diameter stated IS NOT your seatpost diameter. It's the diameter of the seat tube that the seatpost sits within. A 31.8mm seat clamp will most likely be suited to a 30.9mm seatpost. Measure your seat tube diameter to be sure.