Concrete Masonry Units (CMU) comes in a variety of sizes. They are measured by their depth which ends up being the thickness of the wall. The sizes range from 4 inches to 12 inches in depth. There are also half sizes so you don’t have to worry about cutting blocks when you get to the end of the wall. CMUs also come in different weights which reflect the density of the concrete used to make them. There is light weight, medium weight, and standard weight. The weight affects the price of the blocks and the fire resistance and sound dampening effects they offer. There are also different shapes that CMU blocks come in. The best shapes to use really depend on the size of wall you are building, the wall’s use, and its environment.