Sco3797668wrote a review of Mavic Helium Cycling Vest - Men's on April 1, 2010
The vest looks terrific and is made of very nice material - incredibly light and appears to have great wind-blocking capabilities. However, it is sized WAY too small - I'm an average guy (5'10", 175#) and usually wear a medium shirt. I order cycling stuff in large (it's sized for all the racers so you can't expect it to fit regular folks the same way) and this vest was really, really tight in large. I need an XL and I've never bought anything in that size.
In short, order s MUCH bigger size than you normally would.