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