You are bidding on an Eimac 4CX300A transmitting tube.  It is has its original box, which is marked used but good.  This is a general purpose 300 watt output tube, also known as type 8561.  I have not tested it myself, but will guarantee it to be a usable tube.  Shipping weight is 12 ounces.  Please see my other auctions for more interesting radio and audio items, and tubes.