Glass was often the preferred material for storing expensive oils, perfumes, and medicines because it was not porous. The small body and mouth of the vessel also allowed the user carefully to pour and control the amount of liquid dispensed. These small glass bottles are found frequently at Hellenistic and Roman sites, especially in cemeteries, and the liquids which filled them would have been gathered from all corners of the expansive Roman Empire.
To find out more about Roman glass please see our relevant blog post: Collecting Roman Glass.