Set consists of an 'antique' 4 pin UX4 tube socket top with a mating octal 8 pin tube base. Pins and contacts are nicely gold plated. Very handy for tube substitutions; replace an octal based tube with a four pin tube. 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 the base with just a bit of Crazy Glue.