It's an average or slightly above average penis.
A wide angle lens produces a doorknob effect, grossly exaggerating the size of objects as they get nearer the lens.
Objects further seem small in comparison.
Shot close enough, even a difference in distance of 6 or 8 inches can produce this effect.
Without a proper reference, or knowledge of the camera and lens, it is impossible to say for certain.
Its a shot that makes his dick LOOK big... but it could easily be a 6 inch dick.
One clue... his wrist is almost a close to the lens as his dick. You can only see a small sliver of it... but its also huge.