With most Chamois shirts, the size is larger, meaning you should order a size smaller than you usually wear.  With this one, it's smaller.  I wear a Medium shirt, but this shirt in Medium was too small.  The really strange thing is the sleeves.  They are way too long - about three inches extra.  Also, the inner flannel lining stops near the top, & the rest of the shirt is only cotton & it seems thinner than the 9-oz cotton advertised.