Metal collars crafted by Herm Sprenger are a symbol of quality, reliability and security, they are ideal for use in various areas of dog training and everyday life. High quality raw material does not cause allergies and does not stain hair, and 100% quality control makes these metal collars for dogs, some of the best collars in the world. These Herm Sprenger Black Stainless Steel choke chain dog training collars come in Three sizes of wire thickness 2mm, 2.5 and 3mm. All collar measurements include both large end O rings ( collars are measured from the outer tip of one end O ring to the outer tip of the other end O ring). Fur saver and choke chains have to be able to slide over dogs head and ears. Fur saver and choke chains cannot be adjusted, that is why it is very important for them to fit properly. Some breeds have (ex. English Bulldog) their head a lot larger than their necks, in this case chain has to be long enough to slide over dogs head. Please keep in mind that Herm Sprenger collars are manufactured in germany and initial length is measured in centimeters, during conversion from centimeters to inches measurements are rounded to the nearest inch. Please contact for any assistance.