The Hot-rolled Grooved Fittings, also called as PE lined grooved fittings is the kind of composite fittings which is made of galvanized ductile iron grooved fittings UL/FM listed with inside red color polyethylene (PE) powder coating under high temperature. And therefore, it is also called as PE Lining Grooved Joints.

Generally they are used to connect the PE or UPVC-lined Galvanized Steel Pipe or poly steel pipe and PE Powder Lined Steel Pipe.
And the size available is from 1" to 12" (Pipe O.D is from 33.7mm to 323.9mm)
Since the lining covering the interior and ends of the fittings, they are also used for 
abrasive and corrosive service applications.