CPC Subgroup
E21B 15/02 specially adapted for underwater drilling (E21B15/04 takes precedence)
Full Title
Supports for the drilling machine, e.g. derricks or masts > specially adapted for underwater drilling (E21B15/04 takes precedence)
E21B 15/02 Supports for the drilling machine, e.g. derricks or masts > specially adapted for underwater drilling (E21B15/04 takes precedence)