When the device is subjected to the intake manifold vacuum, the upper half of the elastic coating reacts by varying in {HEAD ~ size} to reflect {TAIL ~ the magnitude} of the vacuum 
to reflect
When the device is subjected to the intake manifold vacuum , the upper half of the elastic coating reacts by varying in { HEAD ~ size } to reflect { TAIL ~ the magnitude } of the vacuum
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 REL REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH