The perfect match for the Tung-Sol original. The 6550EH offers excellent linearity, power handling capacity and heat dissipation. Four-pillar construction and mica spacers help maintain a rugged mechanical reliability. Classic tone is sustained at a prolonged, high output. A new leaded glass compound is utilized to maintain vacuum integrity, balanced performance and ensure long life. Great tube for SVT and SUNN amps as well as all Hi-Fi amps.