I have three of these Stoic Hadrons (the Cardigan just arrived)--a medium Cardigan, medium vest, and a large anorak-type hoodie (all purchased when prices bottomed out). They definitely are trim -- not small, exactly, but with not much to spare. For me, this is good, as the medium is efficient and the large (which fits me about like a Montbell medium, smaller than a Golite Bitterroot medium) lets me double up a Katabatic gear down hood under its hood for sleeping.
The arms are perfect for me, in all sizes; the wrist fits well on the large hoodie, a little tight on the medium cardigan, but I imagine that will stretch out.
My only niggle would be that the placket snaps don't seal that well near the top on the cardigan -- the fabric is able to buckle outward and leave an unsealed gap.
But as windshirts with a surprising amount of warmth, or as worn with a quilt for extra warmth, these are great, factoring in their super-low price when they're on sale. Right now the cardigan is in the sweet spot, at 55% off.