The 16340 is a bit like a half-size 18650, or the rechargeable equivalent of a CR123A non-rechargeable cell (for this reason the 16340 is also known as an RCR123A).
But... BEWARE! If you put two 16340s into a torch designed for a single 18650 you'll be subjecting it to twice the voltage. Some torches are designed to take it, but others are not, so you'd be well advised to check the specifications. And if your torch takes more than one 18650 battery don't even think of using multiple 16340s instead. Conversely, the 16340 runs at a higher voltage (up to 4.2v) than a disposable CR123A (3v) – which may melt the heart of your favourite device (and not in a good way)!
However some little torches take advantage of the size of this bijou battery to deliver an incredible performance for their size, since the 16340 runs at the same voltage as full-sized Li-Ions. Unfortunately they don't offer the same run-times, but if you need an eruption of light for a few minutes from a torch the size of your thumb (or a very respectable output for an hour or more) you've found it!
Click on the pictures below to see details, photos and prices and drop me a line to discuss discounts.