METRIC ORINGS ARE TOUGH TO BUY. WHEN YOU CLICK ON THE INSET PICTURE BELOW, YOU WILL SEE THAT THE I.D. INCREASES BY ONE MM AND THE CROSS-SECTION OR THICKNESS INCREASES BY .5MM, UNLIKE STANDARD ORINGS. ONE METRIC ORING KIT WILL NOT GIVE YOU FULL COVERAGE, SO YOU NEED TO KNOW WHAT SIZES YOU ARE TRYING TO COVER. CLICK ON THE INSET PICTURE TO SEE SIZES AND QUANITIES IN KIT.