Personalized Bike Bum Youth T-Shirt. Bike bum text with a heart dotting the letter i in the word bike is a fun gift design for bicyclists at birthdays and holidays. 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.