I had a Giro Hex years ago that fitted great. Bought a Montaro at the start of winter in medium but it was too small so replaced it with a large. With my Buff on, the large fits fine but with it off, it’s a bit too loose I’m now discovering. Fine when standing but as soon as I’m riding, every little bump makes it tip forward. I’ve cut a headband out of an old Buff for now but I might have to get rid of it if it’s too annoying.
Great helmet otherwise, I like the big visor and it’s great that you can move it up right out of the way but I would definitely double check sizing if, like me, you’re in between sizes.