Herm Sprenger Ultra Plus Training Collar with ClicLock and Centre Plate. 

Curogan is a copper tin alloy with a high copper portion and some additives to make the material strong, but without any nickel. Curogan will avoid discoloration of light colored coats on most dogs. Also, the fact that Curogan is absolutely free of nickel will benefit sensitive dogs that show allergic reactions to nickel.

Available in 2 sizes. 2.25mm and 3.25mm