A type,B type &C type drill collar.
Type A(Cylindrical):Be made of Alloy Steel and the craoss sections of the inside and outside pipe are both round.
Type B(Spiral):Be made of alloy steel and the outside pipe has spiral grooves.
Type C(Non-magnetic):Be made of stainless alloy steel with rather low magnetic permeability and the cross sections of the inside and outside pipe are both round.
A type,B type &C type drill collar.
Type A(Cylindrical):Be made of Alloy Steel and the craoss sections of the inside and outside pipe are both round.
Type B(Spiral):Be made of alloy steel and the outside pipe has spiral grooves.
Type C(Non-magnetic):Be made of stainless alloy steel with rather low magnetic permeability and the cross sections of the inside and outside pipe are both round.
A type,B type &C type drill collar.
Type A(Cylindrical):Be made of Alloy Steel and the craoss sections of the inside and outside pipe are both round.
Type B(Spiral):Be made of alloy steel and the outside pipe has spiral grooves.
Type C(Non-magnetic):Be made of stainless alloy steel with rather low magnetic permeability and the cross sections of the inside and outside pipe are both round.
We can also produce based on your requirments.
If you need it,please contact with me .
Audited Supplier 
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