i had to have some tubes in a hurry so i went to the guitar store and suprise. all they had was groove tubes. i said i'll give them a try, after reading a bunch of stuff about how bad they rattle. put them in and wow. i think i have a family of rattle snakes nesting in my amp. i just dont get what people see in these things. the sound wasnt better then the no name made in china ones i took out.