introducing an expandable liquid foam material inside of {HEAD ~ the housing} and allowing the material to expand forming {TAIL ~ a compressible foam} that is compressed and expanded when the helical spring is compressed and expanded 
introducing an expandable liquid foam material inside of { HEAD ~ the housing } and allowing the material to expand forming { TAIL ~ a compressible foam } that is compressed and expanded when the helical spring is compressed and expanded
OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD 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 OTH OTH