Electronic Durometer - Shore D Scale. The 3805D is used to measure the hardness of Rubber, Hard Plastics: Harder grades such as rigid thermoplastics, plexiglass, thermoploystrene, vinyl, sheet, cellulode acetate, thermosetting, Laminates (ie fornica), Other: Paper filled calendar rolls, calendar bowls, etc. (materials that would not normally indent under fingernail pressure, such as a pocket comb or bowling ball).