In reply to nickinscottishmountains:
> Lighter - Arcteryx Proton Lt
That's not designed to be a belay type jacket as such though is it, it's very air permeable and designed to be an active layer like the Nano Air and Polartec Alpha, not as a belay jacket type thing. From Arcteryx you'd be more looking at the Atom AR as a light option.
PS: That site you linked to looks weird, it is a fake seller?
Post edited at 09:19