Casual Canine ™ Preppy Puppy Polos Offer Top Quality At A Great Price Stylish yet classic, these Casual Canine polo shirts feature vibrant colors and a preppy style that will smarten up any dogs' look. Easy-care shirts are made of a cotton and polyester mix for the ultimate in comfort and durability. Machine washable, short-sleeved shirts feature ribbed knit cuffs and two-button collar with reinforced stitching. Preppy Puppy Polos are available in the colors and sizes listed below.