Tri-Block Pair Number of Holes 23 Included Certification None Hole Style 5 Tapped and 18 Untapped Includes 2 Blocks Hex Wrench 5 Mounting Bolts and Case Material Hardened Ground Steel Squareness 0.0003 in Tolerance 0.0002 in Parallelism 0.0003 in Squareness and 0.0002 in Flatness 55-60 HRC Hardness