These batteries are an excellent choice for extra power to high-draw Sony cameras such as the FX6 and FX9.
We combine them into a kit of two along with a charger so that you'll have access to continuous power.
We like this size and capacity, as it's nice balance between portability (being smaller than, say, a BP-U90), but still has more juice than the smaller BP-U30 batteries that most Sony cinema bodies come with.
It's an especially good option for gimbals, where anything BP-U60 size or above would just be too bulky.