Set consists of oxblood octal tube base with gold contacts with a mating very high quality QQQ Japan eight pin black phenolic tube socket top with nickel contacts. Very handy for tube substitutions, for making a 'socket saver', tube testing bias probe etc. My advice is to use Teflon insulated wire allowing enough extra lead length so you can move things around a bit if necessary. The top socket is best affixed to the base with just a bit of Crazy Glue or epoxy suitable for plastics.