otherwise the watch will flop up and down on your wrist. It does fit under shirt cuffs easily, and if u wear the MB&F on your left wrist, the time porthole is on the right side so you will still be able to read the time easily when the watch partially sticks out from your shirt cuffs. Obviously the watch is not for most people IMO but those considering it, it's not unbearable to wear on the wrist.
Cheers,
Anthony