20 pack set 2ml(5/8 dram) micro mini cobalt blue glass roll-on glass bottles with metal roller balls - refillable slim sample vial aromatherapy essential oil roll on (blue) zbfwmx each bottle is made from high impact glass, the glass is thin but durable and not easily susceptible to leaking, scratches, or breaking.<br> so that it could safely stores various substances without damage.<br> these to-go bottles are designed with holding essential oils, perfumes and fragrances, facial and body mists, and various water-based liquids in mind. it is perfect cosmetic accessory for your daily activities and extended travels.<br> how to use it:<br> the bottles come with separate roller/stopper and screw caps. to assemble, simply insert one roller/stopper into the glass bottle after filling and press the stopper down carefully (not pressing directly on the metal ball) until it sits tight. then screw on the cap.