Tube options for MKIII

How much difference is there between different tubes that would work in the Mark-III monoblock?

Was reading that tubes are being blocked-confiscated when shipping to/from abroad and USPS won't carry due to some tubes having mercury.  Has anyone here had issues with this?   I had no problems shipping tubes before but that was a few years back. Plus I triple wrapped tubes in cut cardboard frames.

snav wrote:How much difference is there between different tubes that would work in the Mark-III monoblock?

Was reading that tubes are being blocked-confiscated when shipping to/from abroad and USPS won't carry due to some tubes having mercury.  Has anyone here had issues with this?   I had no problems shipping tubes before but that was a few years back. Plus I triple wrapped tubes in cut cardboard frames.

None of the tubes used in dynaco amps contain mercury.
Mercury was used in older technology rectifiers .
http://www.electricstuff.co.uk/mercarc.html shows some examples.

Yes, but postal employees aren't that informed, so they ban everything.

Any tube of the correct type will work.  Order from a reputable seller and you should be good.
I slapped some JJs in mine and everything works great.