Metal cap used on the earlier 1/4 plugs  for the piggyback cords and used on the earlier cloth wire speaker harnesses on Fender Amps.. There pressed on by 4 points, I have a special made press for that purpose. I have had customers use a screw driver and hammer to make those 4 indentations,by putting the cap on the plug and placing it on a block of wood so it will not kink the cap.  The price listed is for ONE cap.