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What means EH-G

First, this is always a gold pin version available, for all tubes that have the -G in the part number.

Second, for the big triodes, it has additionally a gold grid, and ceramic sockets.

Some info about Gold grids: Improving upon standard 300B grids, which are typically made of pure nickel, the gold plating reduces grid current and adds effective improvements to the overall grid function. Given that all triode power amps draw some amount of grid current whether they're playing softly or at full blast, this stabilizing effect will offer enhanced sound and durability. So go for the gold!

Some info on Gold pins: The question is asked sometimes, why gold pins are necessary. When you feel that gold connections sound better, this is confirmed by many listeners. From the electrical point of view, it can be explanied as well. In case your amplifier has gold plated tube sockets, it is highly recommended to take gold plated tube bases as well.

Here are the combination possibilities you can make, and the results of it.

Please note, for good language, and for best understanding this text, the part on the tube is not the tube socket! The tube socket is the part in the amplifier, the tube base is the part on the tube. Please keep this in mind very good when reading the below table.

Amplifier sockets	Tube bases	Result
Gold plated	Gold plated	Perfect option. Contact surface will stay clean for amplifier lifetime
Gold plated	Non-Gold	Contact corrosion on amplifier sockets is possible, where the gold layer of the amplifier socket will slowly disappear. Considered no main problem, when you clean the tube pins every 5 years with contact cleaner.
Non-Gold	Non-Gold	Not ideal. Contact corrosion on tubes or tube base is possible. Tube pins must be checked and cleaned sometimes. Specially with older amplifiers (like 30 years or more) this will likely become a problem. Cracks or whisker sounds can results from this, and are hard to locate. It is better to prevent corrosion, then having to clean it afterwards. Pin cleaning must be done every 2 years to prevent corrosion.
Non-Gold	Gold plated	Perfect option. Some small corrosion can take place here, but any corrosion will be on the tube pins only. This will be visible as darkened stripes on the tube pins. The "good" part of this is, the gold is an inert material, meaning it will sacrifice itself, and by this keep clean the tube socket in the amplifier. Even when the amplifier sockets were corroded, the gold layer of the tube pins will change this corrosion in clean metal again. This is called "reduction" by chemists. It means any oxide on the amplifier sockets is transferred into clean metal again, but for that the gold layer disappears partially. These are the darkened stripes you see. These can be wiped off again with good contact oil. Since you change the tubes from time to time anyway, this is the best solution, specially for preamplifier tubes, like 12AT7, 6SN7 and similar. These are in the low signal level part of the amplifier and are more susceptible against noise problems as the end tubes.
Warning: We get send back tubes sometimes with contacts "treated" with special, expensive contact material, that is best described as a mixture of silicon grease and very fine silver powder. You can buy this expensive stuff in little bottles from some dealers. This may seem like a nice idea, but is has many disadvantages, and we want to have nothing to do with this. Reported problems are: Grid leakage, due to creapage along the tube base. This will result in heavy bias errors, and burned down tubes. You have no guarantee if this happens. This can can make the amplifier socket dirty, conductive between the pins. This will result in a repair. Conclusion: When you have already used this... remove it!