CPC Subgroup
E21B 17/203 Full Title
Drilling rods or pipes; Flexible drill strings; Kellies; Drill collars; Sucker rods; Casings; Tubings > Flexible or articulated drilling pipes
E21B 17/203 Drilling rods or pipes; Flexible drill strings; Kellies; Drill collars; Sucker rods; Casings; Tubings > Flexible or articulated drilling pipes