These durometers are available in Type a for use with soft rubber plastics and elastomers; Type D for use with hard rubber and plastics such as thermo plastics and flooring; and Type Micro a for materials as thin as 0.03". models are also available with NIST certificate. Mini-dial durometers are compact and easy to carry around the plant or take in the field for on-site testing. The small dial face measures only 1-5/8". scale is divided into 1 point increments from 0 to 100. The durometer holds maximum reading until reset. Ideal for testing hard-to-reach places or for out-of-sight testing. Measures 1-5/8"W x 5-5/8"H. Compliance: ASTM d-2240 did you know.. Type a has a flat cone point 35? included angle. Type D has a sharp cone point 30? included angle. Type Micro a has a sharp cone point 30? included angle. An easy way to Test hardness of rubber, plastic, and other nonmetallic materials.