At Solvit we take our motto No Pet Left Behind seriously. Our line of ramps stairs travel products strollers bicycle trailers and bicycle baskets help pets go places in comfort and style. For an aging Lab with hip dysplasia that is having trouble getting in the car to a frisky Chihuahua that insists on riding in the front seat our products make getting around safer and more enjoyable for pets and owners alike. Do you have multiple bicycles that you will be pulling the Trackr Dog Bicycle Trailer with? Put the extra hitch on your second bicycles so it is simple to just switch out the Trackr Dog Bicycle Trailer from one bike to the other. The Trackr trailers already come with a hitch but it makes it convenient to equip multiple bicycles to accept the trailer. It is just a small piece that that attaches to the rear axel and will not get in the way of normal riding so you can leave it there all of the time. Allows for easy hook up of multiple bicycles. Will not get in the way so you can leave it on all of the time. Attaches to rear axel.