Herm Sprenger | One of the leading manufacturers of metal products for equestrian, dog sport, and boat fittings for over 140 years. Known for high quality innovation, Sprenger is a family-run company in Iserlohn, Germany.SIZE NOTE | Herm Sprenger collars are made in metric measurements, then converted to rounded-up inches for the U.S. market.SIZING, FIT, TIPS | For Prong Training Collars: Measure dog?s neck and add 2 inches. This will be your ?initial? collar size from which you can adjust the collar by removing or adding links to achieve a comfortable, snug training fit.TRAINING COLLARS | Training collars are intended for supervised training sessions when the handler is communicating a desired behavior. All users of training devices should be informed and understand how to use training devices. Do not leave a dog unsupervised or alone in a training device and do not leave training devices on a dog full time. Do not use retractable leash devices or elastic tension leads with a training collar. Do not use training collars on dogs younger than 6 months.KEEP YOUR COLLAR BALANCED | When adding and removing prong links, remember to keep the same number of prong links affixed on each side of the center plate. If the collar fitting requires an odd number of prong links, then make sure one side of the center plate has only one more prong link than the other side. Your goal is to ensure the center plate stays at the front of the dog's neck above the trachea.HOW TO CHOOSE PRONG LINKS | Prong Links can be purchased separately in multi-packs. When ordering, ensure you are ordering the correct millimeter sized prong link in the same metal composition as your collar. This will maintain a consistent tensile strength through out the collar, ensuring proper training communication and collar longevity.CLEANING | Before use, wash metal collars in warm, mild soapy water to minimize fur discoloration.