This is wholly the same as the one designed by @DR95 with the only changes made being widening the 5mm opening to 6mm and removing the embossed cat image. This version allows you to cut slightly thicker cardboard.
This is the version without heat-inserts.
Printed in PLA:
0.4mm nozzle
0.2mm layer height
15% gyroid infill
2 walls
3 top/bottom layers
If you like this remix, please leave a make and a rating for @DR95 as well for their hard work
The author remixed this model.
Made the opening wider by 1mm to fit thicker cardboard, such as some used in Amazon packaging and removed the embossed cat image for a smooth surface