M2 HSS Steam tempered - 62/64 HRc for ferrous cutting applications. 2 pin holes are 11mm diameter / 63mm on center. 2 pin holes are 8mm diameter / 45mm on center. The first number is the outside diameter of the blade, 350mm. The second number is the center hole diameter, 32mm. The third number is the thickness of the blade, 2.5mm. The fourth number is the total number of teeth on the blade, 220 teeth.