Cock Rings Vibrating Cock Rings

Essentially the purpose of a cock-ring is to create a situation where the blood can't escape the penile tissue as easily as it can enter it, resulting in some mens' penises becoming slightly more engorged than normally possible (so, a larger erection, in some).  The body is naturally very good at pumping blood in, but it doesn't really actively pump blood out.  The evacuation of blood is mostly due to the circulatory process of moving the blood in...it pushes it along.  So this concept of engorging by pinching off works pretty well for most men.