Weightlifting bar collar

Collar to hold weights on straight bar around 25mm (1 inch). Has a very tight grip when used with TPU friction piece. I recommend PETG for other parts. You also need one M4 nut and a M4 bolt of at least 20mm long. The nut is friction fit so you will probably need pliers to press it in place. If it is too tight you can use a soldering iron to melt it in place. You can fine-tune the diameter by scaling Z-axis of the friction piece to increase or decrease its thickness. You can of course use any other rubbery material around 1mm thick for friction. I glued the friction piece with Loctite so it does not come off when inserting the collar.