'Cock-balloon'

An option with a condom...

Elsewhere I've been talking about options with tubes, and here's a quite creative one

The way to mount this thing is actually quite simple.
I've put on a condom, and have made sure, that there's enough 'spare room' in front of my penishead, to make the balloon.
Along with my penis, I've made sure that the hose from my air-pump is inside the condom.
Next I've mounted the cockring, which by the way is tight enough, to ensure that the condom is 'sealed' between the ring-inside, and my shaft.
Finally I blow up the condom, by pumping air into it, prior to removing the air-hose.

By the way, a tip for the Mistresses:

This idea features a possibility to ensure that the slave is training the ability to get and keep an erection...
Use a cockring, that is just tight enough to seal off the condom, when he's having a good erection, but not tight enough to seal off the condom when he starts to flaw.

Cuff his hands behind his back, and tell him what will happen, if the balloon-size decreases.

The exercise is actually improving his ability to get and keep an erection, apart from the fact that the erections will become harder..*S*