The PCE-DD-A Hardness Tester is an ergonomic device that checks Shore hardness in gum, plastic and other non-metallic materials. The PCE-DD-A Hardness Tester is used primarily for soft gums, elastomers, natural rubber, neoprenes, casting resin, white PVC, leather, etc. If the material thickness is not enough, it should be tightened on the back with the same material to increase its thickness. Calibration is not an option.