The MESA EL-34 STR-447 is our very best overall EL-34 - It is a premium grade, NOS (New Old Stock) equivalent and our tube of choice in the production of all new Mesa EL-34 powered models - It has a traditional EL-34 tone & feel that is very urgent and aggressive and is an excellent choice for all styles of gain, especially classic rock, alternative rock & metal - This tube is true to the crown with focused low end, crushing mid range crunch and crystal-like highs - This is one of our favorites for authentic British tone - Excellent structural quality provides exceptional consistency and reliability