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