Bicycle trailer coupler compatible with most bicycles, including those with disc brakes, and works with Schwinn and InStep brand trailers. Not suitable for BREEZER style dropouts. Fits QR shafts and 12 mm (outer diameter) solid shafts, approximately 0.48 inch. High-quality iron construction provides a durable and sturdy structure for long-term outdoor use. Precision-designed with a 1/2 inch hole diameter connecting to the bicycle and a 1 inch outer diameter where it connects to the axle. The trailer-side hole measures 1 inch in diameter. A 12 mm straight shaft may require adjustment. This replacement shaft features external threads. Ideal accessory for family biking, allowing your bicycle to tow a child or pet trailer, enhancing outdoor fun for you and your loved ones. Highly wear-resistant and built for excellent durability. Color: Black Material: Iron Package Includes: 2 x Traction Heads Note: Package includes only the items listed. Other products are not included. Note: Lighting and display differences may cause slight color variations between the image and the actual item. Measurement error allowance is +/- 1-3 cm.