The main qualities that you will want to consider when deciding on what material gage blocks to purchase include dimensional stability, accuracy, thermal conductivity, and hardness. Dimensional stability refers to how much a material changes in size over time. Through use and environmental changes, some materials are more susceptible to changes than others. Accuracy is the degree to which a material can be made more precise through flatness, parallelism, and the finish on the surface. Thermal conductivity relates to the coefficient of expansion of a material and refers to the ability of a material to move to the same temperature of another material. This is important, for various industrial parts will come with their own coefficients of expansion. Finally, hardness is the quantitative degree of resistance of a particular material. Depending on its grade of hardness, a material will be more or less resistant to wear or abrasion.