A drilling riser assembly for subsea well installations, the drilling riser assembly comprising: a male drilling riser assembly section, comprising: an internal stab type male main drilling riser connector, a main drilling riser flange having a helically threaded ring on the outer edge of the flange, and a box connector (60,160) having an inner helically threaded ring configured to mate with the helically threaded ring on the outer edge of the flange and having a set of inward facing inter-engageable annular projections and grooves (66,166); and a female drilling riser assembly section, comprising: an internal stab type female main drilling riser connector, a main drilling riser flange having a helically threaded ring on the outer edge of the flange, and a pin connector (80,180) having an inner helically threaded ring configured to mate with the helically threaded ring on the outer edge of the flange and having a set of outward facing inter-engageable annular projections and grooves (86, 186) configured to engage with the inward facing inter-engageable annular projections and grooves (66,166) of the male drilling riser assembly section box connector (60, 160). a male drilling riser assembly section, comprising: an internal stab type male main drilling riser connector, a main drilling riser flange having a helically threaded ring on the outer edge of the flange, and a box connector (60,160) having an inner helically threaded ring configured to mate with the helically threaded ring on the outer edge of the flange and having a set of inward facing inter-engageable annular projections and grooves (66,166); and an internal stab type male main drilling riser connector, a main drilling riser flange having a helically threaded ring on the outer edge of the flange, and a box connector (60,160) having an inner helically threaded ring configured to mate with the helically threaded ring on the outer edge of the flange and having a set of inward facing inter-engageable annular projections and grooves (66,166); and a female drilling riser assembly section, comprising: an internal stab type female main drilling riser connector, a main drilling riser flange having a helically threaded ring on the outer edge of the flange, and a pin connector (80,180) having an inner helically threaded ring configured to mate with the helically threaded ring on the outer edge of the flange and having a set of outward facing inter-engageable annular projections and grooves (86, 186) configured to engage with the inward facing inter-engageable annular projections and grooves (66,166) of the male drilling riser assembly section box connector (60, 160). an internal stab type female main drilling riser connector, a main drilling riser flange having a helically threaded ring on the outer edge of the flange, and a pin connector (80,180) having an inner helically threaded ring configured to mate with the helically threaded ring on the outer edge of the flange and having a set of outward facing inter-engageable annular projections and grooves (86, 186) configured to engage with the inward facing inter-engageable annular projections and grooves (66,166) of the male drilling riser assembly section box connector (60, 160).