This is a circular perimeter tests. This will let you know if your printer is printing circular perimeters properly. Here are the dimensions: Height: 30mm First Circles: 5mm inner, 6mm outer, 1mm thick. Second Circles: 10mm inner, 12mm outer, 2mm thick. Third Circles: 20mm inner, 24mm outer, 4mm thick. Fourth Circles: 30mm inner. 36mm outer, 6mm thick. Fifth Circles: 40mm inner, 48mm outer, 8mm thick. Tip: Be sure to measure with a caliper for accuracy. Be sure to post pictures if you decide to print it! Happy Printing!