16oz amber Boston round glass bottle with 28-400 neck finish. The Boston round bottle is distinctive in its classic shape. Characteristic of the Boston round are its rounded shoulders and rounded base. Glass has high clarity, can be colored, has high chemical-resistance levels, and has extremely high resistance to heat and cold. It is great for storing essential oils. This container is amber, a rich and vibrant orange-brown. In the case of glass, this amber color is made by mixing sulfur, iron and carbon into the base glass. Plastics are colored by using pigments. amber containers are shaded from light amber to almost black. This amber color provides some UV protection for light-sensitive products. This item has a 28-400 neck finish. The first number refers to the diameter (in mm), and the second refers to the closure depth, style and thread. This container can be paired with a closure such as Phenolic cap, Aluminum screw cap, Plastic cap with this matching finish.