Ball Cap Buddies. They are plastic "cages" that they sell in the laundry basket aisle at Walmart, K-Mart, etc.. Simply put your ball cap in the Ball Cap Buddy, put it in the washer with cool water and a small amount of laundry detergent, and let the machine do its work. Leave the cap in the Buddy until it is dry. In the case of wool caps, however, take them to your dry cleaner to handle.