Shows even the tiniest little 'bulge', so better size up!
I'm fairly slender & tall and can usually go with a medium anywhere. To be safe, I still checked the sizing info, which resulted in me ordering a size M.
Sadly, it didn't fit too comfortable for my liking, a bit more on the snug side, so I returned it.

On the feel & quality, it did truly feel like an old t-shirt, very comfy!