Question to 6L6 tube experts


Who can tell me whether the NOS TungSol 6L6 WGB tubes are suitable replacements for Sovtek 5881/6L6 WGC tubes? I am a complete nube in 6L6 variety and I am afraid of making a mistake!
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I didn't think KT66 tubes were an exact replacement for 6L6GB tubes. Thanks for the lead Mcgarick. I'll have to do more research.