The MESA® 5881 STR 425 is a military-grade 6L6 designed with an emphasis on rugged durability and the capability to handle higher voltage requirements. It produces a full bass and rich midrange with tapered highs that lends itself to styles of jazz, fusion and traditional roots and blues music… or any style where tapered high frequencies and greater longevity and reliability is desired. The STR 425 is also commonly used in older, 6L6-based MESA Bass Amps such as the MESA D-180, Bass 400 and Bass 400+ models.