The at least one shut off flap and the body may be {HEAD ~ a single piece} formed of {TAIL ~ a material} substantially the same as a material forming the snap hinge 
formed of
The at least one shut off flap and the body may be { HEAD ~ a single piece } formed of { TAIL ~ a material } substantially the same as a material forming the snap hinge
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH