I made these HangBalls for climbers to train pull-ups and finger strength. There are 3 sizes: 25,32 and 75mm diameter. They have all been designed to trick your slicer into adding more walls inside the balls to make it much stronger.
It fits any rope up to 8mm. Thie a nut in the end and add 2 balls to the rope. Very easy to do. I used some chalk for a better grip.
3D printing settings
Print in PETG or stonger 4+ walls 30-60% Gyroid infill
For fuzzy skin: Skin Thickness 0,25mm Skin Point distance 0,6mm