Personalized Las Vegas 21st Birthday Youth T-Shirt. 21st birthday Youth T-Shirt - Heather with Las Vegas welcome sign that says IT'S MY FABULOUS TWENTY-FIRST BIRTHDAY. Fun and unique for her very special birthday. 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.