Threadrock Big Boys' Birthday Boy 5 Year Old Youth L/S T-Shirt Threadrock exclusive Runs slightly small; consider going a size up Sizing: XS (2/4), S (6/8), M (10/12), L (14/16), XL (18/20) 100% preshrunk cotton; seamless rib knit collar; reinforced neck and shoulder seams; rib knit sleeve cuffs