1.PP Compression Reducing Coupling 2.Type I /blue,black 3.PN10/PN16 4.20* ... When you are connecting pipe with fitttings, whatever, steel or iron pipe and fittings, or PVC pipe and fitting, or PPR ... equal tee, PP 90 degree elbow, 45 degree elbow, PP coupling, PP male adaptor, PP female adaptor, PP saddle, etc. Pressure ... and compensate the part of loss to you . PP Compression Reducing Coupling