Drag bit,Rotary bit,Oil Drilling,Rock drilling,Rotary drilling,Down the hole, DTH bits,Well Drilling,PDC bits,PDC drilling bit Three Wings Drag bits:1. Drag Bits are made according to API Standard or NROD Thread standard or others.2. Various Step and chevron Drag bits are available from 2inch to 17 1/2 Inch.3. There are big markets in USA,Canada,Colombia,Australia and so on.4. There is very good ...