This set is great for those looking for a stretch and to prevent turtling.
The three different weights add variety and can all be worn at once.
They are smooth silicone rings with ball bearing in the bottoms, funny enough they look like flatter testicles I would like to note that the lighter the weight the bigger the rings on the sling are. So you will need to be careful depending on your girth and what you are wearing to prevent embarrassing situations.

The slings are comfortable to wear but should not be worn without care and regular checking in order to prevent damage to the penis. But with three, you can wear all three with ascending or descending weight changes, and you can use them near the head for simple stretch. They can even be used around the testicles for those into that as well.

They can also be used as cock rings and would provide a sufficient grip providing the person had enough girth, but I wouldn't get them as my main cock ring.
For guys who like ball stretching (yes that's a thing), these would be great.

Research on these types of things is minimal, but temporary changes can be made, and I would say the use of these for permanent change would probably depend on your discipline and availability to use them.
Everyone is different, and every problem is different, but don't expect magic and be ready to use these for months for maximum effect.

I can see uses for these if one comes up with a routine and protocol and sticks with it for some time, beware of placement, as you don't want to damage the oh-so-sensitive (and fun) glands beneath the head of the penis.

I got these after my partner had a surgery in the lower area in order to prevent turtling.
He found them comfortable but it took adjustments to make sure they don't slip off while the penis is not erect.
He is on the girth side, but those of slimmer builds may need to add gauze and watch their wearing time.