The MESA® 6L6 STR-443 is a premium grade, vintage-voiced 6L6. They are beautifully balanced, offering a deep low end, controlled, tailored low-mids with a pleasing sparkle and chime on the top-end that provides a pleasing clarity. High quality structural integrity provides consistent, reliable performance, making this tube a great choice in any 6L6 based amp, and for any style of music.