The grid is composed of {HEAD ~ glass} containing {TAIL ~ lead oxide}, and eliminates the spacer material used in prior known grids, and is therefore, an air core grid 
containing
The grid is composed of { HEAD ~ glass } containing { TAIL ~ lead oxide } , and eliminates the spacer material used in prior known grids , and is therefore , an air core grid
OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD 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 OTH OTH