Blake’s cock in this scene always looked like it had the same proportion (and bounce) as Ben Afleck’s scene in Gone Girl, so I’ve always assumed it was a similar prosthetic. When Jenner was on The Glee Project, I didn’t see a whole lot of bulge in the swimsuit episode (granted: pool—>shrinkage!) and in my experience, growers tend stand at attention, which he isn’t much in this clip… so my guess is prosthetic. I just wish his ass be more… bouncy.