I HAVE HUNDREDS OF TIE TACKS, TIE BARS AND CUFF LINKS. I always try to point out any clear blemishes and condition. tie tack/bar: 1.99" x 0.41" (2" x 3/8" or 50.5mm x 10mm). collar bar: none. 0.25" = 1/4" or 6mm - pretty small for standard button holes.
