Guinness "Clover" Bottle Opener Hat (Green). This Officially Licensed Guinness Bottle Opener Hat is the perfect way to always have a bottle opener on hand. This unique Guinness hat features a built in brim mounted opener that is solid and secure. This patina finished bottle opener features the Guinness and is fastened on a beautiful vintage green hat with Guinness insignia. This hat is fully adjustable and features an adjustment band in the the back to adjust the hat to the perfect size for you.