Check the listing for details. 1 2 3 Blocks Precision Tri-Blocks Setup Work Holding Plastic Case PR123. Condition: New. Listed at 44.64 USD. Tri-Blocks 1-2-3 Precision Block Set with CaseIdeal for Precision Layout & SetupEach set consists of a matched pair of 1 2 3 blocks, five 3/8″,-16 stainless steel socket head cap screws, hex key, and shop-hard-molded case.Each block precision ground on all six surfacesCase hardened (HRC 55 60)Surface finish from 6 to 16 micro-inchesSquareness on all sides to within 0.0001″23 holes: 5 tapped 3/8″,-16 ; 18 untapped thru holesThe cross drilling is designed to give minimum weight yet maximum strengthOversized to allow for nominal 0.0001″ / 0.0003″ Made In ChinaTypeTri Block SetNumber of Holes23Overall Length2″MaterialHardened SteelOverall Width1″Includes‎Matched pair of 1 2 3 blocks, five 3/8,-16 stainless steel socket head cap screws, hex key, and shop-hard-molded case.Overall Height3″Model NoPR123Squareness0.0001″