Durometer is the measurement of the hardness of rubbers, elastomers, plastics and foam materials. This term is often used to refer to the measurement as well as the instrument. The hardness testing is most commonly measured by the Shore (Durometer) test or Rockwell hardness test. There are 7 different scales ( “shores”) to measure durometer. The Shore A scale is used for 'softer' rubbers while the Shore D scale is used for “harder” ones. The Rockwell scale is similar but uses a different testing method and is for very hard plastics. The higher the number - the greater the resistance of material to indentation.
It is important to note that the scales overlap but are independent of each other. There are no direct correlations between measurements on any of the various scales. In addition, durometer measurements under 10 and over 90 on any scale are not considered reliable.
For durometers available please check Properties Chart