Bicycle trailer coupler compatibility: suitable for most bicycles as well as disc brakes and and instep brand trailers. It& 39;s not for BREEZER style dropouts. For QR shaft and 12 mm (outer diameter) solid shaft, about equal to 0.48 inch).High quality material: high quality iron, solid structure, excellent structure, outdoor long-term use of high-quality trailer connector.Precise design: the diameter of the hole connected to the bicycle is 1 / 2 inch, and the outer diameter of the part connected to the axle is 1 inch. The hole in the trailer is 1 inch in diameter. 12mm straight shaft needs to be adjusted straight shaft. This replacement shaft has external threads.Family fun: additional trailer coupler accessories connector, family bicycle can be equipped to tow children& 39;s trailer, your child or pet will enjoy the fun of riding a bicycle.100% Band new and high quality:High Wear-resistant and excellent durability.Colour: blackMaterial: ironPackage Contents:2 x traction headsOnly the above package content, other products are not included.Note: Light and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm."