This Brüel & Kjaer Cathode Rejuvenator kit Is part of the renown line of Brüel & Kjaer test equipment.it is in good condition and has seen some small wear over the years. There may be some pieces missing from the kit. These microphones and kits are extremely rare and highly sought after due to it's exceptionally clean sonic response. This unit has not been tested and may not function, for parts or project only. Owned and used by the famous Indigo Ranch Studios, Sonic Circus now has the privilege to sell this hard to find wonder.