These are THE Plastic alternative to Glass Liquid Medical Bottles. PET is a relatively new polymer that brings Plastic containers much closer towards the quality and lower environmental impact of Glass. They afford a robust, light and (according to current science) a much more inert barrier to their contents than other polymers. Having the PP28mm Neck Finish, these Bottles may be Child-resistant, Tamper-Evident, both or neither.PLEASE NOTE: MATCHING CAPS NEED TO BE ORDERED SEPARATELY.