The Guardian Gear 4″ Nylon 3-Way Small Dog Coupler with Nickel-Plated Swivel Clip is designed to make it easy to walk two dogs at once. Made of tough nylon, with nickel-plated swivel clips for long-lasting use, the coupler is available in black, blue, hunter green, and red. The coupler is designed to be used with a leash that has a metal loop (like a carabiner) on one end and a plastic loop (like an M-loop) on the other end.