'D' scale made for hard plastics such as polystyrene, Formica, vinyls, phenolic molding materials, Plexiglas, and hard rubbers. Totally enclosed working parts. When the indentor is displaced exactly 0.100 inch, a special cam arrangement allows a scale alignment of 100. Scale is 240 circular degrees and is easy to read. Scale is well within 1 per cent of the calibration curve. Will exceed or meet requirement specifications of ASTM D2240. Comes complete with carrying case and test block.