Diameter : Product size: Bicycle rear axle fixing hole diameter: 11mm Mounting hole diameter for link trailer: 7mm Diameter of recessed area to which the shaft nut is screwed: 21 mm Bottom plate length: 55mm for children's trailers and most bicycles Weight: 159 g Material: stainless steel Color: Black Scope of delivery: 1x bicycle trailer hitch Portable Easy to install: the tow bar has vertical and horizontal holes. Regardless of whether the holes in your bicycle coupling are vertical or horizontal,they work perfectly for you. Family fun With an additional towbar, both Mommy's and Daddy's bicycles can be equipped to pull the child trailer.Your children will enjoy the bike tour. A bonus: if your kids get tired of driving,you can attach them next to your bike. Material Steel that is strong and safe. Compatible Bicycle mount for multi-compatible compartment, fits most bicycles.