Sorry, I remembered that battery medium wrong.
Well it does say “battery” as opposed to “batteries”. Perhaps they thought they were being more accurate / detailed by saying 2x2600 rather than 5200.
However, I completely agree it could be done better.
And… I have no idea what a ‘wire-free’ battery is supposed to mean.
Especially considering the battery has 4 wires. 
Ignore the other people that don’t know how batteries work.
It’s two 3.7v 2600mAh lithium cells wired in series making it a single 7.4v 2600mAh battery. It has balance wires to monitor each of the two cells voltages and has a temp sensor.