Our Biothane® multi-purpose coupler is designed to be used in a variety of situations. Shorter lengths can be used to couple your dog's collar to their harness. Medium lengths can be used as a coupler or a seatbelt. All you need to do is buckle your seat belt like normal, and then clip one end of your coupler around the strap and to the o-ring. The other clip is then secured to your dog's harness. Longer length couplers can also be used as a free-floating leash splitter. Since the o-ring is not secured in one location, we recommend this only for dogs who don't pull or lunge. Couplers are made using 3/4" Beta BioThane and solid brass hardware.