Why do you call it '2S' when it has three wires? So you buy a "2S" if you have a three-wire balancing lead and a "3S" if you have a four wire balancing lead? How intuitive is that? A little more product description would go a long way and save the customer from having to re-order until they get what they actually need.
yes, they are for 2S batteries.
The red wire goes to the positive, the black wire goes to the negative, and the blue wire goes to the balance port on your battery. these are great to have in your toolbox. you can use them to repair broken balace plugs, or make new charge leads with a balance plug.
Good to cut off to use for balance plug for DIY Lipo packs.
An idea for all the female ends could be multi-charge plug to charge multiple 2s in parallel.
Furthermore for applications of amps drawing under 6A, this can directly replace JST connectors meaning the Lipo balances, charges AND discharges from the JST balance plug - i.e. save weight by not needing the JST connector and wire :)