Regular joint (REG), mainly used for IU drill pipes, with joint inner diameter
Digital connector, a new series, gradually replaces all IF and all except 5 1/2 "FH in API standards. FH connectors are interchangeable with old API connectors, mainly NC50-2 3/8" IF,NC38-3 1/2 "IF, NC40-4" FH, NC46-4 "IF and NC50-4 1/2" IF.
