The three main hardness scales are Shore OO, Shore A, and Shore D. The main Shore durometer scales work in tandem, with one scale picking up where the last one left off. With that said, there is some overlap between each scale, but it is important to note that durometers do not translate directly between the different scales. Each scale ranges from 00 to 100, with a more central range representing the most commonly used measurements. The Shore OO scale ranges from about 20 to 60, the Shore A scale ranges from about 5 to 90, and the Shore D scale ranges from about 40 to 85. A material with durometer of 60OO also can be said to have a durometer of 15A and material with a durometer of 90A can also be said to have a durometer of 40D. Again, these are helpful measurement translations to help understand how the scales interact, but whenever you are switching between types of durometer measurement a new measurement must be collected to ensure accuracy. Durometers are a relative measurement and are themselves dimensionless and so conversions between measurements are not a precise translation.