Personalized 50 Is Just A Number Youth T-Shirt. Happy 50th birthday! 50 is just a number. A BIG number! Fifty years is a long time, you know. 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.