... combines advantages of tricone bit and PDC bit and avoids the defects of them, so that it not only can be more suitable ... suitable for the operation in hard interlayer and other complex stratum where PDC bit is not suitable. SizeBit TypeIn.mm6152.4517, 537 ... , 627, 63717 1/2444.5517, 537, 617, 627, 637 Both new and used are available , we are purchasing all kinds of used ...