Shore D DurometersModel No. PHT-980FEATURES:CERTIFICATION: The units are not designed to ASTM specifications and cannot be certified as such.Shore D scale is for testing the following materials:Rubber: HardPlastics: Harder grades such as rigid thermoplastics, plexiglass, thermoploystrene, vinyl, sheet, cellulode acetate, thermosettingLaminates ie formicaOther: Paper filled calendar rolls, calendar bowls, etc. materials that would not normally indent under fingernail pressure, such as a pocket comb or bowling ball.