Hand Tools
Hardened Steel Precision Gauge 25-50-75mm/1-2-3" Blocks Parallel Clamping Block Set 23 Holes Parallel Block With Screw Wrench for Machinists and Metalworkers(25-50-75MM)
1-2-3''blocks, 23holes. Hardness: 45 steel in good quality. Parallel tolerance: 0.0002mm Squareness: 0.0003/1 Size range: ±0.0002
https://www.bizrate.co.uk/handtools/hardened-steel-precision-gauge-25-50-75mm-1-2-3-oid40436678878.html