S-104b MICA DIAPHRAGM for the Concert and Junior Concert reproducers. The mica is ‘best quality’, clear, and is the EXACT size just like the originals in diameter and thickness needed for such reproducers. The diameter is 1 19/32″ (that is 1.59375 inches) and the thickness is 0.0055 inch. These diaphragms do not have the center hole since most repairmen prefer to drill their own center holes. Note: The $3 price is for ONE mica diaphragm. You may order any quantity at this price.