Boring tool set is made of high quality steel with great match of hardness and toughness, thus prolongs its service life.Design assures superior rigidity for chatter-free boring and precise hole size accuracy.Hardened and ground adjusting screw designed for long lasting and trouble free use.Pacadge Included: 1pcs 3" boring head, 1pcs R8 shank, 12pcs 3/4" boring bars, 3pcs allen wrenches. Boring Head size: 3" Boring Bar Hole: 3/4" Cross Hole Diameter: 3/4" Maximum Offset: 1" Thread: 1.5"-18 Graduations: 0.001 Shank Diameter: 3/4" Thread Size: 1.5"-18When the direction of the dial is reversed, the backlash between the gear train is listed below.Overall Length --- Bore Depth --- Min. Bore3-1/8"---1-1/8"---7/16"3-11/16" ------ 1-11/16" ------ 7/16"4-1/4" ------ 2-1/4" ------ 7/16"3-1/2" ------ 1-1/2" ------ 9/16"4-1/4" ------ 2-1/4" ------ 9/16"5" ------ 3" ------ 9/16"3-7/8" ------ 1-7/8" ------ 11/16"4-13/16" ------ 2-13/16" ------ 11/16"5-3/4" ------ 3-3/4" ------ 11/16"4-1/4" ------ 2-1/4" ------ 13/16"5-3/8" ------ 3-3/8" ------ 13/16 "6-1/2" ------ 4-1/2" ------ 13/16"