Amazon.co.jp: Bike Seat Post, 27.2/30.8/31.6 Lightweight Carbon Fiber Bike Seat Post, Suitable for Most Bicycles, Mountain Bike Road Bike MTB MTN 1.0 x 15.7 inches (27.2 x 400 mm) : Sports & Outdoors
Amazon.com : COCH Zoom Bike Seat Posts Bike Suspension Seatpost 27.2mm 31.6mm Alumium Adjustable Seatpost for MTB Road Bike Mountain Bike Fixed Bike Seatpost (Black+red, 27.2mm) : Sports & Outdoors
Amazon.com : 27.2 mm Bike Suspension Seat Post: Bicycle Seatpost Shock Aluminum Alloy Absorber Damper 27.2 30.9 31.6 mm Seat Post for MTB/ Road/ BMX Bike 27.2 mm : Sports & Outdoors
Bike Seatpost: Extra Long 350/450mm Bicycle Seatpost—Upanbike