I currently use 18650s in lights that use multiples of two of the 123 batteries but I use primaries in my everyday light/headlamp that use a single 123 cell. I couldn't be more pleased with how the 18650s have worked for me & I am thinking about buying some 16340s.

I wish I had experience specifically with the 16340s but I wouldn't expect it to be so different from the 18650s.
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