HHIP 3402-0055 1-2-3 Precision Block Set with Screws & Key, 23 Holes Hardened and precision Ground on all 6 sides of each block; Includes Matched pair of 1-2-3 blocks with 23 holes, 5pc of 3/8 -16 Socket Screws, Hex key Accuracy with Squareness on all sides within .0001 per inch