For a Shetland sweater, it is fairly snug. My jacket size is 39. I tried the O'Connell 40 and the 42. (Their website suggests sizing up.) Both were huge on me. This sweater is a 38, and it is roomy enough. You would not want a skin tight Shetland wool sweater. You would overheat! The science of the Shetland sweater is the air space between the wool and you.The O'Connell sweater is thinner and lighter than a J Press Shaggy Dog.