1 2 3 Building Blocks with Single Hole - STEM Educational Toys for Kids, Perfect for Preschool Learning & Creative Construction Play

USA Made - Matched Pair.

For precision grinding, layout,etc.

• Drilled Hole Size: .500 ~ .501
• Accuracy with Squareness on all sides within .0001 per inch
• Hardened to RC 58-60 and ground to surface finish from 6 to 10 micron inches
• Dimensions: 1 x 2 x 3"
• Parallel accuracy .0001" to .0002"