Cock rings take advantage of the fact that an erection is due to more blood flowing into your penis than is flowing out.  They keep the blood in your penis by exerting a pressure that is higher than the venous pressure but lower than the arterial pressure. This prevents blood from flowing out of the veins of your penis while blood keeps coming in to the arteries thus giving a prolonged erection.  Cock rigs can be very rewarding if they are right for you.  Here are the things that are important.  
1.  It must be comfortable and be so arranged that it provides a good fit.  I like to use a ring with a clitoral stimulator, but after I bought a new one of my favorite model, I found it was not a good fit for my current obsession because of the position of her clitoris so I haven't used it and I use a simple one.
2. Above all, it must be the correct tightness ie: it has to be tight enough to prevent venous blood from flowing out but not prevent arterial blood from flowing in.  One way to be sure that blood is still going in is to find the penile pulse.  These are to either side of the top surface of your penis.  Get an erection and feel around, they are prominent. Then fit the ring on.  Then stimulate yourself to get an erection.  The pulse must still be present.
The final proof is to try it.  If it is working well, you will like it and so will she.

Who cares... They look hot And  I love what they do for a limp set of balls. ….lol Just kidding the men I have used them with have stated that they do Intensify orgasm  as well as prolonging and enhancing the erection.  But every one is different so jump in give it a try.

I haven't been able to find one large enough to fit me.

I WISH!

Seriously, it does enhance the experience for me.  so I say yes.