Exact copy of the original clear glass KT66. The tube that created “The Bluesbreaker Tone.” used in 50's-60's hi-fi favorites such as the Heathkit W-5M and many Leak amplifiers. Genalex Item No. KT66 GENALEXGet yours today; with the security of our many decades of experience and Sam Ash Direct efficient order processing, your satisfaction is guaranteed!