Box Two™ Quick Release Seat Clamps are cold forged and CNC machined from 6061-T6 aluminum alloy. The head of the lever and the face of the clamp are given a proprietary low-friction surface treatment that ensures smooth lever action for the life of the clamp without the need for a bushing. Size: 31.6mm for 27.2mm seat post Feedback:all ok thank you.BOX Two 2 Quick Release Seat Clamp 31.8mm suit 27.2mm seat post Black q/rGreat product fast and speedy delivery A +++BOX Two 2 Quick Release Seat Clamp 31.8mm suit 27.2mm seat post Black q/r ThanksGeelong Bicycles