The MESA 6L6 STR-440
is a premium grade, US equivalent and Mesa's tube of choice in the production of all new Mesa 6L6 powered models - Remarkable bass definition, articulate mids and shimmering highs keep every note amazingly intelligible, with a smooth, creamy character - Premium structural quality provides exceptional consistency and reliability - Amazing for all styles of music.
The STR 440
is a direct (Chinese) replacement for out of production
STR 420's and STR 430's.