Outstanding. So much better than a tennis or golf ball.
Printed for my wife, she has serious muscle pain due to nerve damage in the back. She tested them, and I had trouble getting them back to take the picture :D
PETG, 0.4 Nozzle, 0.14 layer height, 5 walls, 2mm top, 1.5mm bottom, 40% gyroid infill. I wanted these to be as sturdy as possible. (edited)