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