I talked to Merit from RF Parts today (he is in charge of 572 program) and the 572 is far for obsolete. I asked him about rumors of envelope issues and he said it was all rumors that did not start with them. They have been getting regular shipments for 6 months the only "problem" is they are trying to get production rate increased as it is still a bit slow. I handled a tube it is nice and even feels good in hand. Look for them to available in limited first come first serve quantities in a few months with it getting better over time. MSRP is 70 bucks. BTW, Ameritron has put AL572 production on hold until they can get tubes. It seems that Ameritron does not want to pay a higher price for tubes as they bought them direct before but RF Parts have exclusive right to tubes being made so time will tell. The good news is do not retire that 572 amp any time soon. One more thing, RF Parts hi pot tests tubes at 7kv and seeing a very low failure rate.