WeeSpecs two-piece design is made from a very soft hypo-allergenic material and can be adjusted for a custom fit. The inside frame of the goggles seals around the skeletal socket reducing pressure on the eyeball and allows a baby’s eyes to open and close naturally. Preemie size fits head circumference 28cm. WeeSpecs Small fits head circumference 28cm-34 cm, and WeeSpecs Medium fits head circumference >34cm.