The classical version for professional dog training: This training collar in classic styling with assembly chain is the standard version with two rings. Herm Sprenger is one of the leading manufacturers of dog training products, best-known for their quality, reliability, and safety. All products are made in Germany, utilizing only the finest materials and components. Through their continuous quality control efforts over the past 140 years, Herm Sprenger’s training collars are recognized as one of the best training collars sold on the market today. Product Details • Curogan dog training collar; nickel-free, copper tin alloy which benefits dogs that have an allergic reaction to nickel • Avoids discoloration of dogs hair • Distributes correction pressure evenly around the dog’s neck. • Sizes Available: Gauge 2.25mm X 16" (41cm) Gauge 3.2mm X 23" (58cm) Gauge 4mm X 25" (63cm) • Links may be added or removed for proper fit. Additional links sold separately