Review on Precision Measuring with Woodworking Caliber Marking Degrees by Olusola Edwards

Well done. Finds the center of a round stock up to 5/16 inch. It is important to tighten the set screw (possibly finger tight) to ensure accuracy. A wider (1/16 inch) ruler than the one provided will do, but not a narrower one - the magnet will hold it, but the set screw cannot be tightened to secure the narrower ruler.