Curved Concentric Brick

This is a curved brick with an angle of 30 degrees. When 12 are made into a ring, it will have an OD of 12 inches (305mm) and an ID of 9.5 inches (240mm). I used this to make a mold for a modular foundry, but you can use it however you like. Although it takes 12 to make a perfect circle, slightly varying the angle can allow for other numbers as well.