Not sure on sizing.
The neck is a little too small for my liking, especially for the size (XL) I think a better way to provide and idea of sizing is actually state the measurements of the shirt, top-bottom and across the chest. That way people can go to their favourite shirt and compare the sizes to what size this equates to in your shirts. I ordered an XL and I'm normally a Medium to Large. Your XL is almost too small for me.