The koolSoother? teether by Nuby? provides a cool, textured surface for baby to bite and teethe on during teething periods. The cool, resilient surface soothes and stimulates sore gums safely. Engineered with raised, offset surfaces, the koolSoother? teether assists in the eruption of teeth by gently massaging infant"s gums. Colorful shapes are easy for baby to hold and sized for maximum effectiveness as a teether and soother. All Nuby? water-filled soothers use purified distilled water.