Synthetic strap with soft polyester lining for comfort. * Contoured EVA footbed. * INFANT SIZES ARE (from smallest to largest): 3/4, 5/6, 7/8, 9/10. These come with an optional elastic backstrap (as pictured) to keep sandals on tiny feet * KIDS SIZES ARE (from smallest to largest): 11/12, 13/1, 2/3, 4/5. These do not come with elastic backstrap