Personalized Baseball Irish Shamrock T-Shirt. A green baseball with the imprint of a shamrock is a unique Irish themed gift design for baseball players and fans on birthdays and St. Patrick's Day. Wardrobe essential for looking good, 24/7. 5.0 oz., pre-shrunk 100% cotton. Seamless 1x1 rib collar. Shoulder-to-shoulder taping. Double-needle stitched sleeves, bottom hem and front neck. Note: greys are a cotton/polyester blend.