wherein during the initial expansion, the foam material expands between the coils of the helical spring, and within {HEAD ~ a gap} provided between the spring and {TAIL ~ the housing} 
wherein during the initial expansion , the foam material expands between the coils of the helical spring , and within { HEAD ~ a gap } provided between the spring and { TAIL ~ the housing }
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 REL OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL