tiny batteries help with that
i stand by what i said
The real question is: Convoy S2 or S2+? Or Convoy S2 plus plus filter? 
And has lousy aim.
You can see the dried champagne splatters on your dinning room ceiling and walls
We use our UV S2+ with a ZWB2 lens to find puppy urine in carpeting. My youngest son (19) is into rocks these days and has take over the flashlight to illuminate a variety of them.
Always add the ZWB2 filter if you’re serious about this… 
This thread is useless without pictures.
@tactical_grizzly:
If my family ever lives somewhere where we can grow tomatoes again, we'll be using a UV light to find tomato worms.
Sweet!
The S2 has it preinstalled.
I’ve read mixed reviews. Some prefer one over the other.
I don’t own UV flashlights so I didn’t research it.
I'm not very sure which UV LED is used for the Convoy S2 / S2+ now..
Around 2 or 3 years ago, Convoy offered these UV flashlights (which I have ordered before):
1) Convoy S2+ (black body color) with Nichia 276A UV365 LED (700mA) w/o ZWB2 filter installed
2) Convoy S2 (black body color) with LG LEUVA33U70RL00 (UV365 3-watt) (1050mA) w/ ZWB2 filter pre-installed
3) Convoy S2 (grey body color) with LG LEUVA33W70RL00 (UV365 5-watt) (1750mA) w/ ZWB2 filter pre-installed
I have the 3 versions listed above.
However, on checking Convoy's website, it appears the UV365 LED used for these flashlights have been changed:
Convoy S2+ (black) UV365 = still Nichia 276A (??)
Convoy S2 (black) UV365 = "Seoul UV365" LED can't seem to find more specific data (1050mA) w/ ZWB2 pre-installed
Convoy S2 (black) UV365 = "Seoul CUN66A1G" LED (1750mA) w/ ZWB2 pre-installed
I've not tried ordering these Seoul UV365 based Convoy flashlights yet though.
As a side note:
I have a Convoy C8 UV, and the LED it uses is different from the one on my earlier S2 / S2+,
ie. it doesn't look like a Nichia 276A, nor the 2 kinds of LG UV365 on the S2.
Also have a Convoy S12 (triple UV365 LED), but I have not tried removing the ZWB2 filter to check what LED it uses.
Both the C8 UV and the S12 UV come pre-installed with ZWB2 filters.
Malkoff UV drop in uses a Seoul LED
is Seoul better ?
Used mine to find a transmission fluid leak on our old Honda CRV. Lit the tranny fluid right up. I also use mine to check all the hotel rooms I stay in. PSA: Never use any throw pillows or comforters for anything in a hotel room.
Surprising none have yet mentioned disinfecting.
UV light is used to disinfect, 185nm and 254nm being the optimum frequencies –though 185nm disinfects through creating ozone unlike 254nm that kills microbes directly by, I believe, denaturing its DNA. Mercury lamps have a wavelength of 253.7nm, very close to 254nm, so they work well and are integrated into UV-C air purifying systems. While the newer power LED’s have tighter frequencies in UV-B, the light emitted from older 5mm UV LEDs was not as narrow, so a 5mm UV LED that was intended to emit near UV, perhaps with frequencies peaking between 350nm-400nm, may actually also emit frequencies above and below the peak in a wide bell shaped curve. Though intended for black light purposes, if they emit frequencies down into UV-C, even with less intensity than their peak frequencies, they will also disinfect.
I have an old ARC UV flashlight. intended for checking currency or working with identifying minerals, so UV-B or near UV, that I am sure emits some UV-C because I left it on pointing at a toilet in bad shape for most of a day. Hours later, I could smell the ozone that accumulated in the bathroom, and the next day the stuff stuck to the toilet washed down with a flush, leaving bare porcelain where the beam met it.
My hope was a UV flashlight could be used to disinfect water and make it potable, but I think to make it practical (so it wouldn’t take hours and hours), it would need to be a UV-C laser, which would be pretty dangerous to eye sight and skin, as this light will blind and cause melanoma. I have seen little mercury lamps that are intended to be purposed to be placed in a cup of water for disinfecting, but I wouldn’t trust that it can disinfect within minutes… it’s going to do something, but it takes time to kill all the microbes or enough of them to prevent getting sick from drinking the water.
Occurs to me just now, UV black lights are traditionally often used in haunted houses for effect, so that’s something else you can do with them 
I saw the C8 too. I was thinking about picking one but didn’t know which one to get. It would be fun and useful for some things but I didn’t feel like doing a ton of research just to find out which one should I get.
This one looks cool. I wonder if these no name flashlights are any good or complete crap.
You mean this but a flashlight
https://www.amazon.com/SteriPen-Adventurer-Opti-Water-Purifier/dp/B003A1MURC
I have a “Convoy C8 + 365nm UV LED Flashlight with Patented Glass Filter” which uses one or two 18650’s.
It is shockingly bright. I can see where painted walls weren’t properly prepared (off-white walls appear almost black, with primer showing up as whiter areas).
The UV brighteners in steam cleaner detergent is absorbed into some thread in the carpet, leaving odd, weave patterns.
Toilets look like Salvador Dalí paintings, even after cleaning. Might be the special coating on Toto toilets…
Rocks in the landscape have crazy color patterns.
Drivers licenses and money have strong reflectance info.
To answer the question of why they’ve become so popular, I think lately the largest draw has been UV-curing glues used for phone and tablet repairs, and also for acrylic nails. Before that, the pet urine cleaning industry made a big push, and scorpion spotting has always been there. And rocks/gems, but for that the lower wavelengths are usually best (or required to see anything pop…depends on the target).
In addition to the stuff mentioned above, they are also used sometimes in dermatology. Some fungi will fluoresce or become more apparent under UV light (ringworm being a popular mention but also the athlete’s foot and jock itch varieties, and I’ve heard that at times a herpes infection can show up in the skin).
Some heart wood in trees and shrubs will also fluoresce, often green or yellow, which is kind of neat. Many in the legume family will do this. The pith of twigs sometimes lights up a brilliant intense golden yellow color.
Quite handy for leak detection in various closed system fluids, too, but either the fluid will need to have additive in it from the factory or you’ll have to add the appropriate/compatible dye yourself. Automotive and HVAC, limited use in various hydraulic applications.
The low power/small lights are great for folks that need to check identification cards or currency on a regular basis but those types aren’t good for much else.
I read a while back that it can be used to identify certain kinds of wood by the way they shine under UV light. I tried it on a bunch of my lumber stash and it was a cool surprise.
Here’s a link to an article and video:
https://www.wood-database.com/wood-articles/fluorescence-a-secret-weapon-in-wood-identification/
there is stuff that glows besides germs, pee and poop.
some cleaners leave a blue glowing stuff behind
certain waxes and paints do also
So many uses a few I knew about but most I had no idea like the rocks thats very cool. Ill get one to play around with I think it will be cool taking it camping and finding glowing things in the shallow creek. Where we go camping we get fish and little yabbies and what not im sure something in there will glow.
Another use - my neighbor was doing a DIY covid test and it requires UV light, not sure why you couldnt put it in the sun but he asked if I had a UV light, i found a old one that came with some UV glue i ordered years ago and the light still worked. I threw it over the fence to keep distance he reported that it worked!