Because of the simplicity of the design virtually any size round or rectangular or cylindrical cathode may be made, allowing {HEAD ~ designs} for {TAIL ~ direct retrofitting} of any existing cathode 
for
Because of the simplicity of the design virtually any size round or rectangular or cylindrical cathode may be made , allowing { HEAD ~ designs } for { TAIL ~ direct retrofitting } of any existing cathode
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH