What is that silver circle around dicks?

[Yoook]

Look at this post:
http://www.usg-online.com/forums/showthread.php?t=1158

Now what is that silver circle thing around his dick? What does it do?

[NHundielover]

it's called a cock ring. it helps makes your dick larger and harder when you get hard. and although i don't have experience wearing them, i'm pretty sure it gives you a more powerful cum shot.