WeeSpecs two-piece design is made from a soft, hypo-allergenic, light-blocking material that can be adjusted for a custom fit. The inside frame of the goggles seals around the skeletal socket reducing pressure and allowing the eyes to open and close naturally. WeeSpecs preemie fits head circumference <28cm, WeeSpecs Small fits head circumference 28cm-34 cm, and WeeSpecs Medium fits head circumference >34cm.