These blocks are machined from solid white polyethylene providing the reloader with a very durable, easy to clean loading block. Each block is machined to fit the specific cases you reload and has finger grooves machined into the sides to provide a sure grip. Each hole has a slight chamfer for easy case head entry. The “Poly” blocks are dishwasher safe for easy cleaning. We use white polyethylene because spilled powder shows up easily. These 50 round blocks are 1″ thick to provide deeper holes for your cases to sit in. This is especially beneficial when loading larger cases. See chart for the correct size. The #08-4275 block only has 32 holes due to the case head size.