HHIP 4.5 X 3.5 X 3" Angle Plate & 1-2-3 Block Set Matched PairMfr #: 9999 0006 The angle plate is made of high tensile cast iron properly seasoned against distortion The angle plate clamping slots are widely used for machining, layout and inspection The 1 2 3 block set is heat treated and case hardened to HRC 55 to 60 and is hardened and precision ground on all 6 sides of each block These 1 2 3 blocks have an accuracy with squareness on all sides within . 0002" per inch There are 23 holes on each block that