The Shore scales describe how rigid or pliable plastic material are. There are two main scales: Shore A and Shore D. Shore A describes elastomers or rubbery materials. The D scale describes rigid materials. Both scales start with low numbers and increase to higher numbers. The lower the number, the more rubbery or pliable the material. The higher the number, the more rigid the plastic material. Example: a 15 Shore A material is very rubbery. Conversely, an 85 Shore D material is very rigid and leans towards brittleness.