Hi there, my two cents worth opinion,

all above comments are correct, but there is more.

It is the same shape as SONY cammcoder batterry - will fit in plastic groves - and is cheap and is made in China, but there is only one small difference.

Votage is the same, and polarity points to connect battery are the same - and if you check the battery closely you will see positive and negative connectors and voltage accross is 8.35V when battery full. 

Also you will see a third little metal thingy very close to negative connectors.  Let's call it "control" little thingy silver plate - this is the major difference.

The voltage difference on LINE 6 battery on this control and negative battery terminal is 0.1 V,  while in SONY Camcoder  battery NP-F550 is some 3.0 Volts - so that even if connected well it will not work. 

And, for those nutty pepole, who still want more information on this topic - the 0.1 V on variax battery is stable - like real DC power, while SONY was fluctuating - which indicates that there may be a capacitor in there - but myself being to lazy to find out more I gave up. 

So if someone nutty enough - can order on ebay and check with oscilosope or in a simple way just carck open the plastic cover to have a look.

In short - all is the same except this voltage difference that is not suitable for JTV ---

Happy picking