Personalized Irish Shamrock Letter O Monogram Youth T-Shirt. St Patrick's Day gift Youth T-Shirt - Vintage Black has shamrock monogram Letter O design for St Paddy's Day parades and parties with green clover background and black alphabet O. Let the good times roll in a durable T-Shirt that takes kids from school to play in an amazing array of colors. 5.0 oz., pre-shrunk 100% cotton. Seamless 1x1 rib collar.