I read about these undershirts absorbing sweat, and I'm sure they do. But prevent sweat stains? How does this sweat not eventually transfer to the shirt itself? Try this fun experiment at home: 1) put some damp cotton on some dry cotton; 2) watch what happens. I guess y'all have some magical undershirts. At best an undershirt will delay transfer, which is a fine thing. And of course there's that snazzy Don-Draper American-cravat look.