The 6V6 STR 417 is all about classic American tube tone from yesteryear. Extremely sweet & bubbly with a beautifully deep bass & spacious shimmering highs, this tube defines vintage "Deluxe" styled tone and is the standard tube in our California Tweed & Fillmore 25 - It's also a great substitute in the Mark I, Mark IV & Lone Star when used with their "Tweed" Switch feature or in our Triple Crown amplifiers (no Tweed switch necessary). Please see your amplifier owner's manual for correct use of this tube.