I just bought a used jacket. I normally take a M but sized up for layers as Rab is slim fitting and although I am 5'8" I have broad shoulders
Good choice - the medium would have been ideal with just a base for hiking but I bought for travel as well.
That said there is a lot of inbuilt stretch in the fabric, amazing really, and very light.
Typical well made Rab jacket.
The lack of pockets in the Massdrop version wouldn't be a big problem for its intended purpose but I don't quite get tje lack of velcro cuffs.
The sleeves are long - my jacket would best fit a lankier guy. No velcro would mean a trip to the tailor if you are sizing up.
Hood is prettu good, stays up in strong wind and the fabric is definitely air permeable.
All in all a great jacket.