Undershirts aren't something I'm overly picky about.  The fabric doesn't have to be overly thick, since it's going under a dress shirt.  I just want something that is comfortable and long enough that it doesn't come untucked.  These undershirts do OK in staying tucked in, and the cloth is generally fine, but the neckbands are atrocious.  Each one has a horrible overlapped seam where the band was sewn together - easily 1/8 inch thick protruding inwards.  Put a dress shirt on there, and it rubs all day long.

Buyer beware.