Can't have loud crowing? You're in luck. A clever backyarder who wanted both roosters and happy neighbors decided to take matters into her own hands. She designed, tested, tweaked, tweaked some more, and finally patented the world's only collar designed to dramatically reduce both the volume and the frequency of crowing. It has been tested and adjusted for maximum safety, comfort, and effectiveness. Sizing Listed below is typical sizing by breed, but to be accurate you can measure your rooster's neck (under the feathers, close to the skin, lower on the neck) before ordering, then ADD 1.5 to 2 inches to your measurement to provide enough "overlap" on the collar to ensure the Velcro attaches properly. If in doubt, choose a size larger! XS (4 inches) Class A Seramas only. S: (6 inches) Small breeds like Class B/C Seramas, Bantam Cochins, Pekins, Game Bantams, D'Uccles M: (8 inches) Silkies, Polish, Leghorns L: (10 inches) Most large fowl birds, like Plymouth Rocks, Orpingtons, Marans, Cochins, Wyandottes, etc. XL (12 inches) Extra large birds like Brahmas, Shamos, etc.