Baby Toddler Boy I am 1 Year Old Birthday shirt 2T 40% polyester Super comfortable boutique first birthday shirts in vehicle applique for boy toddler. Accented with an adorable trike, this 1st birthday boy tee shirt is available in all sizes so you can find the perfect fit. Ages 1, 2, 3 and 5 60% cotton 40% polyester. Ages 4 and 6 88% cotton 12% polyester.