Up for sale is a pair (2 pieces) of rare vintage ITT S11E12 / 7971 heavy-duty beam power tetrode tubes, brand new in individual white boxes. Manufactured in England, these rugged industrial-grade tubes feature heavy metal base construction, black plates, and original clear ITT glass print. Highly prized in high-end audio for OTL power amplifier designs and series regulator circuits due to their massive current capability and outstanding reliability.

As shown, both tubes are in immaculate New Old Stock (NOS) condition with clear, crisp factory markings.