This is a 4oz clear PET boston round bottle with a 20-410 neck finish. The boston round bottle is distinctive in its classic shape with it's rounded shoulders and rounded base. Polyethylene terephthalate (PET) is of the polyester family and has high clarity, good chemical resistance, high impact resistance, and medium rigidity. PET is also light-weight and is used for products containing essential oils. Sold by the case (100 count).