Sovtek EL84 are extremely reliable and good sounding. The construction has improved steadily over the years. Sovtek EL84 are currently being used by such manufacturers as Fender - Crate - and Peavey. The Sovtek EL84 produce an unbeatable smooth - warm distortion. Excellent replacements in vintage VOX AC-30's and the like. NOTE: Due to the larger diameter of the glass envelope, this EL84 will NOT fit in the following amplifiers: BadCat Model 2R Bad Cat Amplifier Model Black Cat Marshall DSL201 Marshall DSL401 VOX reissue AC15 Budda Superdrive 30