BL-123 Pair of 1" x 2" x 3" Precision Steel 1-2-3 Blocks Go to amazon.com Related posts Top 13 drill guide for 2022 Top 10 best setup blocks 2022 Top 13 machinest square Top 15 machinist level Which is the best setup bars? FeaturePrecision ground. Case hardened.Cross-drilling design for extra strength and minimum weight.Five 3/8-16 tapped holes are provided for clamping. DescriptionHeat treated above 48 Rockwell "C"; .0001 to .0003 over allowance for nominal lapping. Squareness of all sides is within .0002 per inch.