Folding Bicycle Seatpost Swivel Wheel Hidden Sub Wheel 360° Rotation Universal Wheel for Transportation Travel Parking Q81COOTDTYfeatures: The built-in push rod is basically suitable for most folding bicycles. It can be used with or without pneumatic cylinders. No tools required. It is directly attached to the seat post and installed quickly. Once suitable for folding bikes, a booster is installed on the seatpost to help push and lift. 360° universal rotation, free control direction, compact and lightweight. The hidden subwheel is installed inside the folding bicycle seatpost, which is convenient and quick and does not affect the disassembly of the bike. It is not only suitable for folding bicycles, but also can be installed on round tubes with an inner diameter of 28-32mm/1.10-1.26 inches or 25-44mm/0.98-1.73 inch outer tubes, such as tables, hangers, or shelves. Specification: Material: Metal Color: Silver/Black Size: Approx. 3.5x6.9cm/1.38x2.72inchPackage Included: 1x Auxiliary Roller WheelNote: 1. Please allow 1-2cm errors due to manual measurement, please make sure you do not mind before ordering.2. Due to the difference between different monitors, the picture may not reflect the actual color of the item.