Ground on all 6 sides of block, accuracy and squareness on all sides within 0001 " 0002 23 holes includes ( 5) 3 / 8-16 threaded holes for clamping and ( 18) untapped holes for Cross drilling design allows for efficient use of lower weight with strength We 3 kinds optional ( A / B / C), you can choose or more according to your needs chrome steel materials, practical and Perfect for machinists, woodworkers, metalworkers, and more, Manufacturer: sodeber