I have bought 2 shirts made of this material (Pima Cotton) at different times, and both had to be returned because they were too small. It seems that Crazy Shirts should be able to standardize the sizing of their shirts regardless of the material used. In the meantime, I'll have to try to remember to order Pima Cotton shirts one size larger than their regular cotton shirts. After returning and getting the size that fits, I am happy with the quality and feel of the Pima shirts, which are lighter weight and look a little "dressier" than the standard cotton shirts.