Fits the "13-612-7" SPI 12" Caliper, and the "15-719-8" SPI 6" Caliper.  Likely fits others as well, just compare to the shape of the one on your SPI Caliper.  If printing in FDM, I would suggest PLA as you'll likely get the most detail.  I used .08mm layer height on a Bambu Carbon X1-Carbon, and the results were quite amazing for FDM. An SLA (resin) printer will give the highest detail, but may actually be weaker and warper, depending on the resin chosen and printer used.