Rings can be worn both around the penis and around the balls, as well as around everything.
There are rings for behind the glans rim. These serve to keep the foreskin back. They are often worn for long periods of time by men who train their foreskin to stay back. Especially for stretching the frenulum and getting rid of the narrowing in their foreskin.
Rings on the penis base, both in front of and behind the balls, help to make an erection harder. They are also popular with men who have a moderate erection and see it as a problem. In itself it is also perfectly possible to enjoy and cum with a flaccid penis, but it is often an embarrassment towards a partner.
In particular, a penis ring behind the balls must be carefully chosen in size. A little too narrow and the penis can swell. Although with patience it is quite possible to get it off again, every hospital has experience with men who panic with a swollen penis with a ring that they can not get off. If a penis ring is chosen too large and worn longer, there is a risk that it will fall off in public.
In addition to erectile enhancement, the penis ring has another function. He pushes the balls forward. This creates a more attractive bump in the pants. But it also pushes the balls away between the legs. This can be very pleasant in warm weather, when the scrotum is hanging and can be sticky from sweating. In this way, a penis ring of a pleasant size has a similar function as a bra for breasts.
If a penis ring is worn for too long, or is too narrow, the penis can swell. The foreskin in particular can then become thick. Foreskin in general easily swells. The swellings disappear fairly quickly after the ring has been removed. If it takes too long, it will prick in the foreskin and become very unpleasant.
Penis jewelry does not exist. There are only beautifully designed rings in various styles. A penis is such a complex device in shape that no jewelry designer has yet managed to come up with something that makes it even more beautiful.