Black, flexible fitting that makes connection to a sewer inlet easier and less hands-on when the inlet threading is stripped or dirty. Put the 3-in-1 adapter on the bottom of the 4-in-1 and simply press it into the dump station. The ridges on 3-in-1 will keep the sewer assembly firmly in place. The 3-in-1 can also be used without the 4-in-1 adapter, by placing the sewer hose directly in the 3-in-1. Adapter is compatible with 3″ NPT, 3-1/2″ NPT, and 4″ NPT sewer inlets and features wings for easy removal, with holes in the wings to attach a rope if desired