This specification covers two types and three grades of thin biaxially oriented polymeric resin film composed of polyethylene terephthalate (PET, Class A) or polypropylene (PP, Class B) for use in capacitors for electrical equipment. Type I has smooth surfaces, while Type II has at least one rough surface. Each of these types is further subdivided into the following grades: Grade 1, not pre-treated; Grade 2, one side pre-treated to facilitate the vacuum deposition of metal; and Grade 3, both side pre-treated. The physical, mechanical, and electrical requirements for which the polymer films shall be tested on for conformance are as follows: tensile strength and modulus, and break elongation; insulation resistance and conducting paths; permittivity, dissipation factor, and dielectric breakdown voltage; nominal thickness and width; density; melting point; shrinkage; tear and impact strength, and fold endurance; color or clarity; moisture absorption and permeability; oxygen index and permeability; resistance to corrosive agents; heat or solvent resistance, and hygroscopic coefficient of expansion; aqueous extract conductivity; and acidity. Thicknesses of the capacitor films shall be carried out by either the roll weight, ten-sheet stack, or gravimetric methods.