Baseball Caps used to be 100% wool now they are pure polyester.
MLB and its cap manufacturer, New Era, say the new fabric is designed to "wick" away sweat and evaporate it while reducing the stains, odor, shrinkage and fading that come with wool.
I know you are wondering, "but what's the deal with the ugly spring training caps?"
The batting practice caps are "stretch fit," not individually sized like the regular-season caps, and sell for $28. They are 62% polyester, 38% wool, also billed as having wicking properties. A stretch band is visible on each side of the cap above the ear.
"I'm not a big fan of them," Atlanta Braves pitcher Tim Hudson says of the new batting practice caps. "They have that little different color-flap (the stretch band) above the ear and it looks like everybody is running around with a do-rag under the hat."