The final 5F8-A Twin-Amp version released in 1958 and produced into early 1960, had become the crowning achievement of Fender fifties amplification. The 5F series Twin utilized the finest heavy duty Concert Series Jensen P12-N Alnico V blue-dome loudspeakers (conservatively rated in 1957 at only 18 watts apiece). In the day, players would rarely ever open such high-fidelity amplifiers to their distortional limits. These "high-power" tweed Twin amps would deliver peaks up to 80 plus watts of power when turned high. With such bursts of volume energy, often these top-of-the-line Jensen speakers would fail, and sometimes even burn out (smoke) voice coils. Many well used Twins have replaced speakers today. Keith Richards has used these late model, high-power Twin amps on Rolling Stones tours with his own special design Celestion Alnico (similar to the G12-80) speakers to insure optimum live efficiency. Today, the famous 5F8 series Fender Twin amps with their warmth of tone and rich rock & roll harmonic edge, command the highest price of any Fender amp ever built.