{HEAD ~ An apparatus} for simultaneously forming {TAIL ~ a plurality} of closely spaced, parallel grooves having a web between them in a thin walled tube is described 
for simultaneously forming
{ HEAD ~ An apparatus } for simultaneously forming { TAIL ~ a plurality } of closely spaced , parallel grooves having a web between them in a thin walled tube is described
HEAD HEAD HEAD HEAD HEAD HEAD REL REL REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH