Product description: The diameter of the bicycle rear axle mounting hole: 11mm Connection trailer mounting hole diameter: 7mm The diameter of the recessed area where the shaft nut is screwed: 21mm Base plate length: 55 mm Weight: 158g Material: stainless steel Type:Child trailer Model: See picture Color: Black Scope of delivery: 1x bicycle trailer hitch with safety pin coupling steel coupling adapter 1.Effortless Trailer Attachment: This bicycle trailer hitch makes attaching trailers to your bike a breeze,saving you time and effort. 2.Reliable and Sturdy: Crafted from stainless steel,this hitch provides reliable and sturdy performance,ensuring stability during your rides. 3.User-Friendly Design: The hitch features an intuitive design that allows for easy installation and removal,enhancing convenience and usability. 4.Wide Compatibility: Designed to fit a range of bicycles and trailers,this hitch offers broad compatibility,making it suitable for various setups. 5.Ideal for Family Adventures: Specifically designed for child trailers,this hitch enables enjoyable and safe family adventures,creating lasting memories.