In terms of an inexpensive set of toys these cock rings are OK. We don't have a whole bunch of experience using cock rings simply because we've never seen the need for them. Both guys have plenty of stamina and neither have problems maintaining an erection. Still, it never hurts to try something new.

This set of two stretchy TPR cock rings are adorned with "jewels" crafted out of the same material. We got the blue/clear set and the gem doesn't sparkle or add anything to the ring itself except a spot of color. The other ring with the white jewel has a clear heart dangling from it. These are truly novelty items.

The first ring measures about 1/2" unstretched and around 4 1/2" stretched. The total toy measures 3 1/2" in diameter and 2 1/2" in length making it a rather substantial size. It has a large blue "gem" on the top made from colored TPE. This ring fits pretty firmly on Sigel's average girth and does lend a bit more firmness though we were unsure if it would prevent much in terms of premature ejaculation or loss of erection. Still it did cut off some blood flow without causing discomfort and Sigel did enjoy the experience. The ring was a bit too large on the base of his penis to make actual intercourse much fun for me because it got in the way of deep penetration. The "jewel" was large and caused a bit of discomfort when hitting my vaginal opening. He likes using the ring during a blowjob or during masturbation as it increases those sensations very pleasantly but for actual sex it wasn't as nice a feeling.

The second ring has a white "gem" instead of a blue one, again made from TPR. It also has a dangling heart on a little string of TPR at the base. I am unsure how this little addition adds to the toy unless it is meant to be purely decorative. It doesn't hit against anything during play and can get tangled in hair making it a bit unpleasant for both of us. Our solution was to keep it lubed with a water based lube (this is TPR but it can react as though it was silicone threatening to melt in the presence of silicone lube) and ignore it. Eventually we just trimmed it off with a sharp pair of scissors.
The ring, itself, is also about 1/2" unstretched (minus dangly bit) and 5" stretched. It is a bit softer than the other ring and therefore can stretch a bit more. It has a 3" diameter and a 3 1/2" length (with dangly heart).

Both rings are phthlates-free, hypoallergenic and latex free. Being made from Thermo Plastic Rubber they are a bit less porous than their jelly counterparts and can be cleaned with soap and hot water or a good toy cleaner. They are heavy and substantial but should be able to accommodate all but the very largest of girths easily.
These rings come packaged in a clam shell sort of plastic sleeve that is easily opened and when the insert is removed can serve as a storage box though it won't be the most discreet method of storage.

Sigel isn't much interested in testicle play beyond a bit of stroking or licking so we didn't test whether they can stretch to accommodate the testicles as well as the penis and they do not come with a testicle ring.

These were a fun introduction to cock rings for both guys. They are soft, user friendly and didn't cause the guys any pain from outrageous swelling or restriction of blood flow. Yup, we had heard all the horror stories about cock rings and we were happy to find out that they weren't true.
After four months and a couple dozen uses they aren't showing any signs of wear and tear. They are still supple and crack free. The gems are part of the ring itself so there isn't an separation of them either. This is just a good beginner set of rings.