Comfy Clothiers 5 Metal Collar Extenders for Dress Shirts 10mm (3/8-inch button diameter) metal collar extenders made from 100% zinc alloy Get a 1/2-size of extra room, or daisy chain two together for a full size of extra comfort 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! 5-pack of the best quality premium metal shirt collar extenders (5 pieces)