The 12SL7GT is a glass double high-mu triode vacuum tube designed for low-level audio amplifier applications, phase inverters, and voltage amplifiers in audio equipment and series heater-string circuits. Featuring an 8-pin Octal base layout and a 12.6V heater rating, it provides high voltage gain with separate cathode connections for each triode section. Available in new old stock (NOS) and tested used conditions.