Dogs My Love Triple Chain Martingale Prong Dog Pinch Training Collar 6 Sizes Made of high quality chrome plated steel for durability and resistance to rust and tarnishing Sizes specified in all the way opened and closed positions. Available in 6 Sizes For proper size please measure the circumference of dog's neck and make sure it is not less than "closed" measurement. Also make sure you choose a size (open position) that will fit over the dogs head Triple chain, wire gauge specified for each size Aesthetically appealing, practical and easy to use dog training collar