The dropper is made of glass which is thick and durable so that it can be used repeatedly. The rubber bulb has strong suction and can absorb liquids well. Moreover the dropper and bulb can be taken apart for easy cleaning replacement and storage. There are clear and readable scale lines on the surface of the dropper allowing you to measure the volume of the liquid precisely. This package includes graduated eye droppers and rubber bulbs. Its main use is to transfer liquids such as essential oils acids etc. It is widely used for accurate easy measurements. Its material is glass with clear scale lines on the surface of the dropper which is very practical and reusable.