Walmart's Description:

This combination set is great for the woodworker and includes a mitre square head, center head, and protractor head on 12 In. stainless steel blade marked in both inch and metric measurements. The protractor head has a built-in spirit level and allows any angle between 0 and 180 Degree to be worked. Centering head makes it easy to find the center of round work, making it ideal for turners. All heads are removable and adjustable.