How it's made. Ten PETG blocks, 45 mm square, 12 mm tall per number (the 10 is 120 mm). Each has a low plateau on top that sits in a pocket under the next, so stacks don't slide but no joint adds height - the flat rims meet. The top of every block is a second color with the numeral and a ten-frame cut through it; a groove rings the block at every unit. Made face-down, no supports; one filament change colors all ten faces.