Copper base, XRF set of 22 discs (7 mm), see BS-110B-7MM, BS-14500-7MM, BS-172Be-1-7MM, BS-360A-7MM, BS-464A-7MM, BS-482A-7MM, BS-510A-7MM, BS-544A-7MM, BS-623A-7MM, BS-630A-7MM, BS-642A-7MM, BS-655A-7MM, BS-675A-7MM, BS-706A-7MM, BS-715A-7MM, BS-863A-7MM, BS-903B-7MM, BS-922B-3-7MM, BS-929-7MM, BS-938-1-7MM, BS-954A-7MM, BS-955C-7MM