How do cock rings work?
Penis erections are caused by blood travelling into the penis through blood vessels deep in the core of the penis and becoming "trapped. Applying something like a cock ring around the base of the penis, or around the penis and testicles, helps keep the blood "trapped" in the penis by not allowing it to flow back out.
Cock rings have benefits and drawbacks. For one thing, many men report that cock rings make their penis more sensitive to touch. This can be exquisitely wonderful, or it can make someone who struggles with premature ejaculation very unhappy. Having said that, other men feel that the cock ring actually decreases the sensation on their penis tip, allowing them to last longer (experiment to find out which way this goes for you). A cock ring can make the time spent after the first ejaculation very pleasurable, though, since cock rings slightly decrease sensitivity of the penis after ejaculation/orgasm has happened, and can allow for prolonged intercourse.
Some men wear cock ring just for the fun of the changes in sensation, while other men find that they enjoy their firmer erections - it can make the difference between a "soft" erection which makes penetration more difficult, and a "firm" erection.
Because cock ring restrict blood flow, we suggest wearing them for no more than 30 minutes or so at a time, just to make sure you're not cutting off blood flow to this important body part.