Professional quality precision ground steel and case hardened to RC 55-62 on all six sides
Squareness on all sides within 0.0003"
23 through holes (5 tapped 5/8"-11 TPI and 18 plain)
Overall size is within +/- .0003"; Flatness and parallelism within .0003".
This is a matched set (2 each) of professional quality 2-4-6 blocks They are precision ground and case hardened to RC 55-62 on all six sides. They contain 23 each 5/8 inch through holes (5 tapped with 5/8-11 threads and 18 untapped). Overall size is within +/- .0003". Flatness and parallelism are within .0003". Squareness on all sides to within 0.0003". Pairs are matched to a tolerance of 0.0002". There are 2 pieces per set.