URBEST10-pack Collar Extenders,Metal Shirt Collar Extenders 10mm (3/8-inch button diameter) metal collar extenders made from 100% zinc alloy Add up to 1/2 size to any shirt collar. Discreet extensions disappear completely under any neck tie... its a hidden wonder! Easy fit removable expanders - they simply loop around your shirt's existing button, no sewing required! 10-pack of the best quality premium metal shirt collar extenders (10 pieces)