According to this link http://shatnez.n3.net
Caps/Hats: Requires testing when fabric is wool, tweed, or linen-look. Genuine wool "Kangol" caps do not need testing.
The only other link I could find that was related was on the Yeshiva world.
New Era hats are very popular hats so I figured I would ask on here if anyone has any experience with them. I know shatnez can be a tricky thing and something that normally doesn't have it still potentially could. But has anyone had any of their wool hats tested for shatnez? They are probably the most popular brand of fitted hats in the United States. Some of the official MLB hats are 100% polyester so I am guessing one wouldn't have to have those tested. But it seems like over half of New Era's hats are 100% wool and I would like to know if rabbis or organizations had something to say about New Era hats, specifically.