LittleLeaves Big Boys' Sun Protective Shirt Chameleon UPF 50 fabric blocks over 98% of ultraviolet radiation with no chemicals. Made with a bamboo/cotton/spandex fiber blend of 67.5% bamboo, which is naturally hypoallergenic, moisture-wicking, odor resistant, antibacterial and antifungal. Tagless and incredibly soft. Graphics are printed with water-based inks; a competely chemical free shirt. Perfect for chidren with sensitive or eczema-prone skin. Comfortable, relaxed fit. If you are unsure about what size to order, or your child is in between sizes, it's better to order a bigger size.