This is just a stupid-simple design for a part I needed, that I figured I'd share just as a quick pick-n-print option for those who are too lazy to make their own. This is my first creation, and upload.

The seam points are set for random, so that your chases of a break are reduced.

Goes on a set of metal Everlast dumbbells. The original rubber spacers on these get brittle and break apart really easily. So, 3D printing to the rescue!