A good quality, low cost super capacity battery for the Handset 3, F.I.Z. adapter, and all of our other adapters.
In our tests, a fresh one powered a handset II for 4 times as long and is about the same size and weight as the original. How? Lithium Ion technology, much more powerful than the old school stuff. In the heat of battle, you don't have time to ask yourself if the one you are reaching for was charged or not. That's why ours have an instant reading power level indicator, so you will know for sure that the one in your hand will do the job. As any rechargeable battery gets older, it's capacity dwindles, and its run time gets shorter. Our batteries are so inexpensive, that you can afford to replace them more often when they start to poop out. They are expendables, after all...