This is the part needed to connect a Schwinn or InStep trailer to your bike. It is called a coupler, but it acts like a trailer hitch for your bicycle. It allows a trailer to be connected and reconnected on a daily basis without tools. All trailers usually come with the coupler that works with that trailer, but it can be helpful to have an extra installed on additional adult bikes, so different riders can take turns pulling. The installation requires the removal of the nut that bolts on the rear wheel. Once it is on you will be able to hitch and unhitch the bike before or after a ride easily. Comes with three parts; coupler plate, lock washer and a locking pin. The 25-SAO75 model coupler fits Schwinn and Instep trailers manufactured after October 25, 2016 (AF). If your trailer was made before, 10/25/16 look for part number 25-SA074A to be compatible with your trailer. If you are not sure of the date of manufacture of the trailer, look for a date code on the tow bar of the trailer usually on a sticker. Look for a #2 stamped in the metal of the tow bar to confirm that it was made after 10/25/16.