6922 Tube Question

I need to replace a pair of tubes in my VAC Signature.  They are 6DJ8 6922's.  Though I've had tubed pre-amps for years, this is my first tube replacement.  So I have a real newbie question.  Are all 6922's interchangeable?  Can I use any 6922 or must they be 6DJ8 6922's?

ps - ya, I know, bad time to need tubes given the world situation.