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