Ok. This is done with injection. The man has had an operation (I forget what) leaving the tubes that connect his testes to his urethra in his penis open. He is taking advantage of this by poking a needle with a saline solution into his scrotum. When he is masturbating, the muscles at the base of his cock hold the solution in. But, when he orgasms, they let loose, and as the over-inflated scrotum acts as a balloon, it pushes most of the fluid out. Watch as his balls go from truely enormous to just average. It's safe to say that this man will have an infection very soon and will wish he had never done this. But it hot to watch!