{HEAD ~ A feature} of the invention relates to {TAIL ~ the material} used on the contacting surfaces of the base member and the flaps 
{ HEAD ~ A feature } of the invention relates to { TAIL ~ the material } used on the contacting surfaces of the base member and the flaps
HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH REL REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH