"In September of 1950 Tung-Sol introduced the 5881, an uprated and industrial version of the 6L6GA with a 23.5 watt plate dissipation, opening the doors to the hi-fi movement of the 1950s. This rugged tube also found a home in the '59 Fender Bassman and servo amplifiers used in B-52 bombers. In 1955 Tung-Sol raised the bar of high fidelity with the introduction of the 35 watt 6550, which could deliver 100 watts with a pair in push-pull configuration. This tube was used in the Dynaco Mark III and Sunn amplifers."
"New Sensor now" reissues "the Tung-Sol KT120, which has a plate dissipation of 60 watts, making it the most powerful tube in the 6550/KT88/KT90 family. A pair of these tubes in push-pull configuration can deliver power levels of 150 or more watts. When used at the parameters found in existing 6550/KT88/KT90 circuits, the Tung-Sol KT120 is impervious to overload, delivering peak power with extreme reliability and long tube life. However, taking advantage of the higher current handling capacity of these tubes, a very unique and super powerful and stable amp can be designed using the Tung-Sol KT-120."