Compatible with popular 8-pin tubes such as EL34, KT88, 6L6, 6V6, 5881, 6550, KT66, KT100, KT120, and 7027, this tester allows technicians and hobbyists to perform precise bias current tests easily. A1: It works with EL34, KT88, 6L6, 6V6, 5881, 6550, KT66, KT100, KT120, and 7027 tubes.