Has anyone made a cock ring ? What materials used? Did it work as good as expected.

A shoelace. Yes.

Tried that and loved it, just looking for something new to try

"O" rings. Available in all different sizes at the hardwate stores.

I macgyvere'd one out of a shoelace as a teen lol. I had it looped around made it adjustable & everything, could tie up my shaft and around my nuts i used to tie up my horny little bone till it was purple lol.

my current cockrings are actually silicone rings that are used to indicate beer bottles (like at a party) so u know what drink is yours. They are the best silicone rings ive used (all the sex shop ones ive bought break) and I go a box of thm 12 for $2 at a dollar store! Im still on my 1st one over 2 yrs later

Do the handcuffs count?

You need good thick cord and it helps to shave.

I've cut PVC pipe to about 3/8 long (wide) smooth the edges and works great.
prefer orings though, but I still hope to find more to experiment with

Agree with previous poster, stainless steel o rings are available online at very low cost. Get the thickest wall size you can and try a few diameters. I have one that's perfect for me and wearing it feels fantastic both for masturbation and sex. Makes me very hard and thick which my wife enjoys for anal. Highly recommended.