If it is your first ring: stretchy silicone, and go a size looser than you think. Silicone gives, and it comes off under pressure, which is the entire safety margin. A ring should feel snug and not tight. If it hurts going on it is too small. Use water based lube to put it on, and read the beginner's guide first. It walks through getting one on and off, timing, and cleaning in more detail than a collection page should.
If a plain ring has never been comfortable: try a teardrop sling instead. Three openings spread the pressure across the shaft and each ball rather than pinching everything into one loop, and the shaped base carries some of the load. It is the fix for the specific complaint that rings dig in.
If you want to wear it longer than a few minutes: look for a soft, wide, low-profile ring. Thin hard rings concentrate pressure into one line. Wide soft ones spread it out, which is the whole reason the comfort-focused C-rings exist. Thirty minutes is still the limit.
If you are looking for a white or clear cock ring: nobody manufactures a true white one, and translucent is the closest thing that exists. The frosted Ice colorway on the Hunkyjunk Slingshot is the pale, near-white option. If it is the look you are after rather than a particular material, that is the one to open first.
If your partner is the reason you are buying: get a vibrating ring, and check where the motor sits. Top-mounted reaches the clitoris during penetration. Bottom-mounted reaches the perineum. Both are worth owning and they are not interchangeable. See the couples vibrators for the overlap.
If you are between sizes: buy the set, not the single. A three-piece silicone set costs about what one ring costs and settles the sizing question in one purchase instead of two.
If you are thinking about metal: do not, unless you already know your exact size. Metal has no give and no escape route. This is the one place in the store where the cheap mistake has a medical ending.
If you want it to survive more than one night: rechargeable, not battery. The watch batteries in cheap vibrating rings die after a couple of hours of use and usually are not replaceable, which makes the ring disposable whether or not it was sold that way.
