Features: Package Include: 1 Lock Pin, 1 Coupler, 1 Lock washer. Easy to Install: Just need few minutes to install it on quick-release bike. The diameter of the hole attach to your bike is 0.5inch. The diameter of the hole attach to your trailers is 1 inch. There are vertical and horizontal holes on the trailer coupler, so whatever your bike trailer coupler holes is vertical or horizontal, which works for you perfectly. Fit almost most bikes and trailers With an additional coupler attachment, you can tow the trailer in turn and no need to exchange the bikes they ride. Specifications: Material: Aluminum Alloy Color: Black Size: (Approx.) As Picture Shown Weight: Approx. 152g Package Includes: 1 Set Bike Trailer Attachment note: 1.Please allow 0-1cm error due to manual measurement. make sure you do not mind before you bid. 2.Due to the difference between different monitors, the picture may not reflect the actual color of the item. Thank you