Test Tubes manufactured by Caplugs Evergreen are made from polystyrene or polypropylene. Polystyrene tubes provide clarity and are appropriate for use with mild acidic (except oxidizing acids) or alkali solutions, alcohols (except higher alcohols) and salt. Polystyrene Tubes withstand up to 8,200 x g. Polypropylene tubes are more chemically resistant and are appropriate for use with organic solvents and stronger acids (except oxidizing acids), alkalis, alcohols, chlorinated & aromatic hydrocarbons (except xylene) and ketones. Polypropylene Tubes withstand up to 10,000 x g