This valve medium gain (45 gain) which can be replaced in certain amplifiers by 12AX7 (100 gain) to have a sound blues for example or for products that request (although you would first have to consult the manual to see if it is compatible to 100 %) gives very good sound, light, low noise and although it is manufactured in Slovakia, their sound is 100 % American. In the words of the manufacturer: "Smooth, velvet-like sound. Vintage-vibes galore, great upgrade for that special kick Fenders lacking." The perfect choice for quality and price. Before being sent is checked with vacuum tube tester Orange VT - 1000!