10 ml roll on bottles with stainless steel roller balls, 6 pack, cobalt blue aguder these high quality, cobalt blue, glass roll on bottles with stainless steel roller balls are the most convenient and economical way to dispense essential oil blends. 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 blue glass provides protection from potentially harmful light and the convenient size makes it perfect for travel. how to use? 1. first time using alcohol or pure water cleanup and dry by airing. avoiding hot water! 2. transfer oil/liquid from another vial or mix a blend of your own in this bottle. advices: for best results, dilute essential oils with at least an equal amount of carrier oil. 3. after the oil is in the bottle, place the roller ball insert in the opening. press the insert down firmly until securely connected (try to not push directly on the roller ball itself). be careful, and hold tightly to the bottle during this process. 4. please note that roll-on bottles containing liquids should be stored and transported in an upright position to prevent leaking.