I wanted a collar for my weights that I designed. There were a few different designs available but they didn't work. I first printed the olympic sized design from brianpowell24, https://www.thingiverse.com/thing:3655644. I wanted something to touch first and this was a great model.

My bar diameter measured 24.00 mm and I had 5.25 mm thick rubber on hand. I'll include the step and stl files so you can start your own design based on it. Model is also included in Fusion 360 format at this shared link.( https://a360.co/2X8HVo4 ). The rubber sizes were 17 x 20 mm and 20 x 22 mm to insert in the pockets on the ID.

I used all 3 mm dia hardware; two 30 mm long, two 10 mm long and one 14 mm long plus the five plain nuts.

The pivot arm may benefit from being printed in a flexible material, but I have yet to test it. My pivot arms break after about a month of use.