I tried my first cockring when I was probably 25. At the time, I was visiting the adult bookstore where I worked the night shift. We had a guy come in and asked if he needed tokens for the booth area (we didn't use tokens, the machines took quarters). He was about my age, very friendly and visiting from Washington DC. We chatted for quite a bit, mainly about the local gay scene. He pulled me over to the new gay porn release section and asked me if we had any more videos of the guy on the cover. I told him I didn't recognize him, I wasn't sure if we did. He said that was his ex-roommate. His other roommates and him had heard the (soon to be ex) roommate had been doing porn, but they had no proof. But they got tired of him always begging for money from them and never helping to pay the bills, so they kicked him out. He said that was the first time he had proof that he had done porn. I told him to hold on and I would grab the tape (this was back when a majority of our movies were on VHS, DVD was just starting to become popular for porn).
He told me that before we watched the movie, he wanted to know where our cockrings were located. I showed him the selection we had, which I now know was very small. He bought the basic 3 snap leather cockring. He then asked for a pair of scissors and trimmed off the last snap. I asked him about the cockring and he told me liked it a little bit snug. He told me he would show me later.
I took him to one of the private rooms and we watched the movie with his ex-roommate. Turns out while his ex-roommate was good looking, he was super boring sexually. We both gave up on watching him/the movie. He then pulled his pants down to put on his cockring. He showed me how it fit and how tight he liked it on his dick. I noticed that his dick plumped up quickly after he got the ring on. We flipped through the channels until we found a gay movie we both liked. We played around and I told him I really enjoyed how hard his dick stayed the entire time. He then took it off and put it on my cock. It was obvious that the ring was a bit too small for me, but he got it on me and it made my dick grow rock hard. I did love how it made me thicker and harder. But it was a bit too small and it did start to hurt. I left it on because I really liked it but my dick started to get dark red/purple after a while. So I took it off. Later that day, I went and bought my own cockring. I got the same 3 snap leather one but I did not trim off the last snap. It felt much better and didn't hurt.
Since that day, I have bought MANY cockrings. I usually only wear them for sex, but I have worn them for a couple of days with no problems. My favorite is a ring that goes around the base of your cock and it has a leather strap that goes under your balls and comes up and snaps on either side of the ring at the base of your cock. It came with a hard plastic ring, but I found if I wore it for a long time, the ring would bruise the base of my cock sometimes. I found a soft rubber ring, that wasn't very elastic and replaced the hard plastic ring. It fit perfectly and felt great. Unfortunately, the leather strap started to fall apart and I have never been able to find a replacement.
Right now I have a silicone ring that is perfect. It has enough pull that it can be pulled open and slid over my cock and balls with no problems. When I am wearing it, it fits snug and doesn't hurt. It helps create a nice bulge when I wear it under my shorts/pants.