Conforming to your head with four-way stretch fabric, the Mountain Hardwear Stretch Ozonic Ball Cap offers an excellent fit that won't inadvertently slide off when you're playing outdoors. Upgraded over traditional ball caps, the Stretch Ozonic features a 2. 5-layer Dry. Q Active fabric that's highly breathable and waterproof. This 2. 5-layer fabrication sheds outside moisture while allowing perspiration to rapidly evaporate, meaning you'll stay pleasantly dry from the inside-out without overheating or sweating profusely.