It is probably impossible for there to actually be a non-iron linen shirt.  Make one of those and you get a 5-star rating.  Overall, this is an excellent shirt -- and I love the way that it feels.  My guess is that this product should be ordered in +1 size.  I ordered an XL but I usually wear an L.  It fits great.  I would say if you really think you need an M, you should go for the L unless M is already your +1 size in other garments. I would buy this item again -- when I iron it, btw, I use sizing, not starch.