I wear a 40 reg, and this blazer runs really big. It might be one or two sizes too large. I will be returning, but doubtful I will exchange for a smaller size. Not as nice as I thought it would be.
I really like my tropic-weight blazer. Here in the deep South, I'm always on the lookout for things I can wear to the office in the summer that are light and cool. This one fits the bill. I'm probably going to order a second one in another color very soon. As other reviewers have said, it runs big. So, unless you're planning on wearing a sweater under it, the next size down from your regular one would probably work just fine.
This is a have-to-have sport coat for those occasions when you need to tweak things a little. It has a timeless look and works well with khakis or jeans. It is perfect for a cool evening and a great item for the business traveler. Be prepared for a quick trip to the tailor shop. The sleeves tend to run long.
