I love watching my wife's BF fuck her. He's pretty thin, but muscular and you can see his PC muscles and taint really well. Its super hot to watch it flex and quiver right before he ejaculates. I watch it from behind and massage his really pronounced PC muscle when he pauses to edge it a little. I press my fingers against it and get under them. When he starts, I pop him out and put my mouth on his head and watch his balls tighten and his endless throbbing. Its a lot, but I haven't gotten myself to swallow it yet.. just spit.