M:Part Threadsaver Seatclamp This better-quality seat tube clamp secures your seatpost in place. A technically advanced seat tube clamp Rotating thread insert prevents possibility of thread damage and bent bolts Black anodised aluminium alloy with stainless steel hardware. Neat, light and very functional. Available in the 3 most common seat tube sizes: 28.6, 31.8 and 34.9mm external diameter.