Right at the beginning of the movie, Michael Fassbender is naked in bed. As he leaves bed, we get a quick glimpse at his penis.
Soon after, 2 minutes in the movie, Michael Fassbender walked naked in front of the camera and we get a clear good view at his big uncut penis. We also see his firm butt at that moment.
4 minutes in the movie, Michael Fassbender walks again naked in front of the camera. He is showing us a nice chubby, with his dick head starting to pop out of the foreskin.
5 minutes in the movie, we get a hot scene, filmed from behind of Michael Fassbender peeing and shaking his throbbing dick.
6 minutes in the movie, Michael Fassbender is jerking off in the shower, but we don't see much.
68 minutes in the movie, Michael Fassbender is making love to a woman. We see his muscled butt.

Jack O'Connell is flashing his cock in that movie. It's brief but we can see his uncut dick. Jack O'Connell is somewhat erect, reasonably thick but not that long.