The red flag for me is that when he stands, the cam angle shows it hanging, but seems very calculated to never show the base of it. Same thing with the angle when he's sitting. I notice that in a lot of gallery pics here too.
For me to think it's real I'd have to see the base of his dick, where the pubes are. This is where you'd see either his real dick sprouting out or (more likely) some fake one slipped over/attached/strapped on/held onto.
In the sidebar of other vids on that page, I clicked on one called "Marine" and saw very clearly (to me) that the guy in THAT vid seemed very hung, very real, and very unambiguous in showing it. He shows exactly what I need to see to determine if it's real or not.