It's a pretty clear clip, you can clearly see the jizz coming out of the hole, you can see the skin moving on his penis, and you see it go from hard to soft, so you know that's real too. He also lets go of it and you can see that there are no tubes or anything delivering fake cum. This guy cums more than I pee for goodness sake!!!! I doubt that this is natural considering the swollen state of his balls, i am curious what he might have done in order to make this happen, not that i would ever try it myself, i don't want to break my equipment! Maybe someone on here has some insight.
There are also a couple slightly similar videos if you click the related vids, showing guys with unreal cum volumes, none are as much as this dude though.