I HAVE HAD THIS TUBE FOR A LONG TIME. Oops. What is it use in? I have not seen it on any parts lists or price lists of the usual sellers so don't know what it is it's use. Ray EIMAC 8187 REPLACEMENT NSN 5960-01-005-1192 65W Tetrode transmitter tube I dont know where its used. 73, Jeff KG4RZM