The 6K6G and 6K6GT are low-power audio output pentodes introduced in the late 1930s for transformer-coupled audio power output stages in radio receivers and compact power amplifiers. Featuring a lower plate current draw and reduced heat dissipation compared to the 6V6GT, the 6K6 family was widely specified in battery-operated, console, and tabletop receiver designs where power consumption efficiency was essential. The 6K6G features a classic ST-12 shoulder glass envelope, while the 6K6GT uses a compact T-9 tubular glass shell. Both variants operate on a 6.3V heater and fit standard 8-pin octal sockets. Available NOS and tested used.