bpa-free water-refillable : hygienic, no need to worry about water bacterial infection. chilling the teether in the domestic refrigerator to comfort the discomfort feeling while teething. hollow design : promotes baby’s hand and eye coordination by grabbing and gripping movement. different bumps textures : enhances babies’ control ability of jaw and teeth movement through sucking, biting and chewing. two stage design : developed with different need through the deciduous teeth development. Item comes in assorted color (Pink or Blue).