FireFli Flashlight, retail $24.95*
Manufactured by Key Gear Corp. (URL no longer valid)
Last updated 09-06-11

The ZA-4 FireBug - I mean - FireFli is a very small keychain flashlight that features a white LED in the end, which is powered by four #10 zinc-air hearing aid cells in the barrel.

The barrel is supposedly airtight when the FireFli is turned off, so the batteries won't self-discharge too readily. When the FireFli is turned on, air can enter the barrel and react however it reacts with the zinc-air cells, allowing the flashlight to function.

It comes in a stainless steel body, and its LED protrudes through the end like the light portion of a firefly's butt.

The FireFli is labelled as being the "world's smallest flashlight". It measures 1.5" long (not including the split ring), by 0.25" in diameter.

* Manufacturer has apparently gone down the tube; thus the FireFli is no longer available.


To use the FireFli, remove it and the four hearing aid cells from the package first. The small package containing the cells was stapled to the inside of the FireFli's package; the FireFli itself was glued to the front-facing portion of the inside of the package. Feed the FireFli (see below), remove any glue residue from the FireFli's barrel (a fingernail was enough to do the job here), and then the FireFli will be ready to go.

Turn the tailcap counterclockwise (as if unscrewing it) 1 to 1 1/2 turns to turn the FireFli on, and turn it clockwise (as if tightening it) until it stops turning to turn the FireFli off.

When the FireFli is turned on, the tailcap has a loose feel to it. This is intentional; as the FireFli has to admit air to the zinc-air batteries which power it. This is perfectly normal, and is nothing whatsoever to be concerned about.

When you need to feed your FireFli, unscrew and remove the tailcap, toss it in the john, and flush it away...O WAIT!!! YOU'LL NEED THAT!!! So just set it aside instead.

If necessary, tip the barrel into your hand, and dispose of or recycle the four cells that come out as you see fit.

Insert four new #10 zinc-air hearing aid cells into the barrel flat-end (+) going in first, being sure to remove the tab from each cell before placing it into the barrel. These cells are very small, and stacking them on a table would be more difficult than just sliding them one-by-one into the barrel. Be certain they do not go into the barrel backward. Once all four cells are in, screw the tailcap back on.
Aren't you glad you didn't flush away that tailcap now?

The zinc-air cells are touted as being "environmentally safe", so you should be able to dispose of them and not have to worry about mercury, cadmium, or other heavy metals contaminating the environment around landfills.

Here is a photograph of the small package the batteries came in.

Measures 5mA on my DMM's 2A scale.

I started a battery discharge analysis on the FireFli around 7:00pm PDT on 07-12-04; the machine will poop out a chart when the batteries are expended (if I queer the test, I'll have to start another when I get more #10 zinc-air cells). Will it really last for 80 hours, or will it crap out before then?
Only the CBDSRDM knows.

(Update, 07-13-04):
The FireFli continues to just chug along. An hour or two after I started the test, the arbitrary reading was 0.106 (it started at 0.184), so I figured it would be circling the drain by morning. Not so. As of 11:19am PDT on 07-13-04, the reading is 0.109, and it's been stable all night. Whether this is a characteristic of the zinc-air cells or a regulation circuit of some type in the flashlight remains to be seen.
As of 7:17pm PDT same day, the arbitrary reading is 0.117 and still holding steady.
As of 9:02pm PDT same day, the arbitrary reading is 0.107 and still holding relatively steady.
As of 10:09pm PDT same day, the arbitrary reading is 0.105 and still holding relatively steady.
As of 7:57am PDT next day, the arbitrary reading is 0.109 and the damn thing is still chugging along.
As of 10:54am PDT same day (07-14-04), the arbitrary reading is 0.112 and still holding. This is approximately 40 hours as of this writing.
As of 2:22pm PDT same day, the arbitrary reading is 0.111 and still holding relatively steady.
This is still above the 50% intensity point (the half-intensity point is 0.920), so the little FireFli really is all it's cracked up to be.
As of 5:01pm PDT same day, the arbitrary reading is 0.105 and still holding relatively steady.
As of 6:24pm PDT same day, the arbitrary reading is 0.101 and it looks like it's very slowly starting to circle the drain.
As of 8:10pm PDT same day, the arbitrary reading is 0.100 and it's still holding relatively steady.
As of 9:32pm PDT same day, the arbitrary reading is 0.097 and it's still holding relatively steady.
The half-intensity point won't be reached until the reading drops below 0.092.
As of 7:08am PDT next day (07-15-04), the arbitrary reading is 0.025; looks like it's whirling down the commode now. Actually, around 10:50pm PDT last night, I noticed it was reading 0.041, so the decline started sometime after 10:30pm PDT last night.

And here's the battery discharge analysis chart.
The FireFli runs for about 50 hours to 50% intensity, and about 68 hours overall.
At the end of the test, the LED could be stared directly into without discomfort.

(Update 07-16-04)
After resting for about a day, the brightness is back up. Measured 4,120mcd, which is very close to its new battery measurement of 4,140mcd. So if your FireFli poops out, tighten the tailcap all the way, allow it to rest for awhile, and it will provide more light.

The FireFli appears to be a durable instrument. It was whacked 12 times against a steel rod, and was not damaged in any manner I can see. It also functions the same way now as it did when I first took it out of the package and fed it.

The FireFli is water-resistant as long as it is turned off and the tailcap is tightened until it does not turn any more. When the light is in use, the tailcap seal is broken so that air can get to the zinc-air cells inside; this nullifies any water-resistance the FireFli might have when it's off. Water will enter through the flashlight's tail end when it is turned on and then dropped into water or heavily rained on.

There is a drawn and colored picture of a firebug - er - a firefly on the front of the package; for some reason it looks madder than a piss ant, like it's very angry at something.
Maybe somebody lit its butt on fire.

Beam photo at ~12".
Measures 4,140mcd on a Meterman LM631 light meter.
This is an acceptable value for such a small flashlight, and for the amount of current it uses (5mA).

Test unit was purchased at Lifestyle Fascination on 07-05-04, and was received today, 07-12-04.
The FireFli is labelled as being made in the USA if that matters to you. It matters to some users, that's why I mentioned it.

UPDATE: 03-04-09
I went to perform spectroscopy on the diminuitive little FireFli, and it no longer functions - not even when known-new #10 hearing aid cells were installed in it. Therefore, that dreadful "Failed or was destroyed during/after testing" icon will now appear next to its listings on this website.

UPDATE: 09-06-11
The FireFli is no longer being manufactured -- apparently the company that made it went down the tube.
To that end, I have removed the links in this eval. to the company and to the retailer I made my purchase from, and also added the dreadful "" icon next to its listings on this website, denoting the fact that the manufacturer no longer makes the product.

Durable stainless steel case
Water-resistant when turned off
LED is not overdriven - should have a long, comfortable life

Not water-resistant when turned on
Tailcap has a "loose" feel to it when turned on

    PRODUCT TYPE: Keychain flashlight
    LAMP TYPE: 5mm white LED
    No. OF LAMPS: 1
    BEAM TYPE: Circular, hotspot surrounded by two rings surrounded by corona
    SWITCH TYPE: Twist tailcap on/off
    BEZEL: None
    BATTERY: 4x #10 zinc-air hearing aid cells
    WATER- AND PEE-RESISTANT: Yes, when off only
    SUBMERSIBLE: Unknown/TBA (not when turned on)
    ACCESSORIES: 4x hearing aid cells, medium split ring
    SIZE: 1.5" long (not including split ring), 0.25" diameter
    WARRANTY: Lifetime


    Star RatingStar Rating

ZA-4 FireFli Flashlight *

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