Presented in two packs that are ostensibly dual 6GB (3 x 2GB) sets, per-module capacity is, obviously, 2GB.
Right now, 4GB modules remain relatively scarce. As a result, whilst it is possible to source a three-module pack, totalling 12GB, you will pay through the nose for doing so, if you can find them in stock.
We're actually a little nonplussed that 4GB modules haven't become prevalent, as Kingston showed off a 24GB (6 x 4GB) setup back in February this year,
Whilst part of the high-end HyperX range, the modules also fall into the ValueRAM category. Kingston is pricing the KHX1600C9D3K6/12GX pack at £280, including VAT, making them competitive with the likes of Corsair - and just over double the price of a standard 6GB (3 x 2GB) DDR3 kit.
In terms of validation, Kingston says it has tested them on an ASUS P6T Deluxe and Gigabyte X58-UD6.