What fittings have flats (HEX) on the outside?
The necessity for flats, or ribs, is to facilitate the removal of the freshly molded part for the molding machine and tooling. Fittings with internal threads are required to resist the turning of the tooling core during the unthreading process when coming out of the molding machine. The flats work to prevent the fitting from spinning with the core. Flats are replaced with ribs or sometime the geometry of the fitting prevents spinning. Parts lacking internal threads do NOT require the unthreading action of a core, and may not have the flats, unless the same tooling is used to make a threaded version of the part.
