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