6, Cobalt Blue Glass Roll on bottles with stainless steel roller balls & black caps. 1 Dropper included Perfect for essential oils, perfume oils, or other liquids. Safe, secure and convenient packaging. Perfect for travel, and conveniently fits in your purse. Cobalt Blue Glass Protects Against Harmful UV Rays These high quality, Cobalt Blue Glass Roll-on bottles with stainless steel roller balls are perfect for use with essential oils, perfume oils, and other liquids. Snap in the roller-ball by gently placing the roller-ball in the bottle and then firmly tighten the cap until the roller-ball snaps in. Use the roll-on bottle to apply the perfect amount of product each time. Remove the roller-ball by applying pressure with the cap. The beautiful, Cobalt Blue glass provides protection from potentially harmful light and the convenient size makes it perfect for travel.