Personalized Faux Rhinestone 21st Birthday Youth T-Shirt. 21st birthday Youth T-Shirt - Kelly Green with a shimmering, glittering, sparkling, silver, FAUX rhinestone number 21. Perfect for her 21st 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.