This is a matches pair of 123 Blocks with 11 holes. They are made of hardened tool steel (RC 56-60) and precision ground on all six sides. Overall size within +/- 0.0001" (one ten thousandth of an inch). Flatness and parallelism within +/- 0.0001" (one ten thousandth of an inch). Squareness on all sides to within +/- 0.0003" per inch (three ten thousandths of an inch). Pairs are matched to a tolerance of 0.0002" (two ten thousandths of an inch). There are two (2) pieces per set. Approximate weight per block: 492 grams/1.07 pounds.

Hole arrangement: 5 each 5/16"-18 tapped holes (3 on the 2” x 3” face, one on the 1” x 2” face and one on the 2” x 3” face) arranged for fastening blocks to a surface or to each other for conversion to angle plates and various fixtures. Also included are 6 each 3/8” holes with 1/2” deep counterbores to allow bolts to pass through block faces to threaded holes keeping bolt heads imbedded within the block with no exposed hardware. Multiple attachment configuration are possible using 2 each 5/16-18 machine screws.

Approximate weight per block: 492 grams/1.07 pounds