These batteries are high-capacity compatible units for many Sony video cameras. If your Sony camera is any of the above it can use these batteries to power it for many, many more hours than can be achieved with the normal unit. In theory on some models you can get to 20+hrs of run-time.
In theory it is like-for like with the Sony NP-F970. It is also larger (but compatible) with the NP-930 & 960.
Basically the third party version of this - http://www.amazon.co.uk/Sony-NPF970-CE-Rechargable-Battery-InfoLITHIUM/dp/B0007CYW5A
Asking for £14 per battery including p&p
I have three of these batteries for sale. They are manufactured by Cameron Sino and have the model name CS-F930.
2nd Class Royal Mail postage is included
Add 70p for recorded delivery