when there is a risk of infection and in patients with intolerable ...The information below provides a general overview to help you choose the right material for your project. #1. Crushed stone #1 is the largest of the crushed stone grades and includes stone that is between 2-4 inches. This materials is great for larger jobs or for filling in larger holes. #3. Crushed stone #3 includes stone between 1/2 and 2 inches.There are two crushing methods: "stone-on-rock" and "stone-on-iron". Application: "Stone-on-Stone" is suitable for abrasive materials with medium-hardness and above. The finished product has a better grain shape and a little more powder content; "Stone-on-Iron" is suitable for materials with low abrasiveness and lower than medium-hardness,