12 Inch DTH Bits QL120 Minimum Hole Size: 11.875″ Number of Splines: 16 Height of Foot Valve Above Strike Face: 2.770″ Length of Shank: 7.12″ Bearing Surface Diameter: 7.373″ Mincon DTH Hammer: XP120QL SD12 Minimum Hole Size: 11.875″ Number of Splines: 8 Height of Foot Valve Above Strike Face: 1.700″ Length of Shank: 7.12″ Bearing Surface Diameter: N/A Mincon DTH Hammer: XP120SD