... future Milled tooth bits1,Soft formations(114-117)These bits are designed to drill the softest formations such as soft shales,red ... medium formations(121,124,126,134,136,137)These bits are designed to drill formations such as shales, medium soft limestone, Medium ... ,Medium to hard formations(213,214,215,217)These bits are designed to drill formations such as hard sandstone, dolomite, and broken ...