Very good tube
I ordered a quad for my Fender Twin 135 watt. They were matched well by the tubestore. Construction seems sturdy and professional. They allowed my amp to come to life. They have clean, detailed, rich harmonics and a low noise floor. Its a very balanced sound. Fun to play through. They sounded great at the Fender factory bias setting. My Twin was set up to run them at 48% plate dissipation. I ended up biasing them to 55%. That setting is a happy medium that works nicely for clean guitar playing as well as the more rocking stuff. Just a touch of subtly compressed warmth there if you want it. Heavy Les Paul tunes sound quite spectacular with higher bias settings. I haven't tried the SEDs or the 7581As but I would certainly recommend these tubes for the price.