properly fitted cockrings hold MORE blood in your dick during erection.

In doing so, they increase girth and can add nearly a quarter inch to your length

They make the veins more pronounced, which some women really enjoy ( naturally ribbed for your pleasure)

And they can cause a borderline pain sensation that some men find really fantastic, while other find that it enables them to hold out longer...

that's why.

PS take them off promptly when you are done...

YOu can wear a slightly looser fitting one longer... but the size that really makes your dick swell you want off to allow proper blood flow thru your most vital tissues.