A spout for a flexible bag adapted to hold a liquid, the spout adapted for coupling with a connector having a rotatable spout adapter with an internal thread. The spout has a substantially cylindrical body with an outer surface, a spout opening, and a spout axis. The spout further has at least one flexible tab attached to and protruding radially distal from the outer surface of the cylindrical body of the spout. The tab has a top side that is substantially perpendicular to the spout axis, a bottom side opposing the top side, and a leading edge for engaging the thread. Additionally, the spout, has an undeformed tab length that typically deforms upon engaging the internal thread of the spout adapter.