The sizing is based off average baby size if your little one is bigger or smaller for their age then consider going up or down a few months.This Infant Zoo Animal Romper is designed for newborn boys and features a cute faux two-piece play bodysuit style. Made from 100% polyester, this green romper is decorated with zoo animal patterns, perfect for little ones who love animals. The outfit is comfortable and breathable, suitable for all seasons, including autumn, winter, summer, and spring. The brand IURNXB offers this adorable outfit in the Boys department, making it a charming choice for dressing up your baby boy.