Nice looking vest, and super light. However, what is with Castelli's sizing these days ( both in bibs and tops)? I have never worn anything but Large with Castelli over the years and a large in this is more like a regular castelli medium. Definitely size up- I should have but decided to wear it, It doesn't really give much due to the fabric.
One cool feature is that is packs down to an included zippered bag for easy packing in your jersey pocket.
It does fit a bit short as others have said, particularly in the front, so it is not a vest that you can really use for running or other sports which is kind of a bummer.