There are extra support bars to tighten the system to the  tube bottem. Also very nice made is the socket, of red-brown material, with solid brass sides.  The brass is very good quality, and if you want you can polish it shiny with normal metal polish or car polish.  The tennis ball glass is very nice made, and this is a very nice piece of glass blowers work. They are hand made, and not made on machines, like normal 6SN7.   They have the quick heat-up cathodes of the GT's.   Very attactive priced!   Download the pricelist from the menu! 

FAQ:  Do they sound better? The answer is: Yes!   The reason is very simple.  These tubes have no mica connection from the tube inner system to the glass.   This eliminates a great part of the microphonic effects.  Since inside the glass is vacuum ( -hopefully ;) the ONE AND ONLY way for sound waves,  to reach the tube inner system,  is through and via the tube base and socket.  There is no other path!   The chassis gives a lot of damping to that.  Any mechanical sound waves, must now follow the long and difficult path  through the tube base. Anything that would pass, is damped by the heavy brass ring around the base.  This is the function of the metal base.   This tube is made with real HiFi requirements in mind.    Throw away your tube dampers. 

Interesting about this 2A3 is, that it was inspired on the legendary AD1,  and they just put two systems in parallel.   In this version the tube can be  bought under many Chinese brands.  The Chinese have started making this tube 50 years ago, ane never stopped making it,  until today. 
 

Designed for Hifi and Guitar amps. Really perfectly  made tube, with nice big getters.  The  tube looks better than on the picture.

The 6L6 is no real pethode,  but a beam tretrode which works like a penthode.  A typical American tube from the great days of the juke boxes, and later a very popular tube for guitar amplifiers. 

Be aware that tubes when uses as guitar amplifier tubes,  wear out a lot,  and loose their good sound after some time.  These tubes are low cost,  and it pays off to change your guitar quiter tubes once a year,  to keep the sound like new again.  For this price you can not play with bad sounding tubes! 

Classical version of the 6SN7 ("what goes in is what comes out").   If you are looking for several types of 6SN/, trying out different sound,  these are worth it also.   They are constructed like the very early 6SN7's from the 1940's,  with the old style internal construction.  The later constructions had machine pressed glass bases like the EL34 has.  The earlier types have  hand made glass bases. You can recognise the older construction by the taller glass, and lower microphony.  And yes.... these have the old type construction. Hand made.  

The only real 5U4G from new production. There is no other tube like this, made  new.    It's amazingly low cost,  works excellent,  and you can not see the difference with  the vintage USA Coke bottle tubes, like RCA or Sylvania.