There are cockrings which are snug or tight, intended to promote erection, for use during sex, masturbation, etc. Then there are ones that are looser, which are more useful for all-day wear to improve appearance. I've seen some guys who seem to be able to use a single metal ring for both purposes, but I suspect that is because they gain a lot of girth at the base when they become hard. For the rest of us, wide, soft, rubber rings are best for extended wear. Be sure to lubricate the ring and your skin before application, as lube is important for extended comfort, and use real premium lube, not something you found in your kitchen. Also, some cheap rings are made of plastics which are toxic or cause irritation. But from a reputable brand, a real dealer not random scamazon vendor, and look for a CE mark on the package (indicates conformity to the European health and safety laws, but sometimes faked by we-don't-give-a-shit cheap brands) so you know the material has been tested for bio-compatibility. If you can, buy in person from a store that will at least let you touch and feel the material and stretch before you buy. (Some stores, like Mr. S, even let you try them on.) If you must buy on-line, read the description carefully, and make sure you are ordering the right size for a looser fit. Stores that have quality merch include:
https://www.mr-s-leather.com/sex-toys/cock-ball/stretch-cock-ball-toys
https://shop.oxballs.com/main.sc
665 Leather Neoprene and Fetish Clothing: Cock & Ball Flexible