Made from mild steel and high quality chrome plating, the Dog Collar Check Chain from Ancol is very reliable. Each link on the chain is welded, making for extra strength and durability. The unique design of the chain means that every time your dog pulls whilst walking; the chain will tighten slightly, teaching the dog to come to heel. Check Chains should always be worn under supervision. Ancol Check Chains come in a variety of lengths and thickness. Fine Check Chain, Suitable for Small Dogs. Medium Check Chain, Suitable for Medium Dogs. Heavy Check Chain, Suitable for Large Dogs.