Amazon.com: Bike Seat Post Clamp, 2 Styles of Aluminium Alloy Seatpost Collar Fit for 25.4/27.2/30.8/31.6mm Bicycle Seat Post (Black, 31.8mm) : Sports & Outdoors
MTB Bicycle Seatpost aluminium alloy Road mountain bike Seat post diameter 25.4/27.2/28.6/30.9/31.6*400mm Bicycle accessories - AliExpress