Lights, knives, watches, lighters. Yep, all Man Things that make ya broke.
I sold an X6 and SK68.
The X6 was used twice, when purchased and to test before selling.
I have come to the realization that shelf queens take up space and cost money so are not worth it.
The SK68 was nothing special and i also rarely used it. My most used lights are my Moon RC2 and Olight S2.
I have no UV lights, is this one a good light if only buying one UV light for my collection?
https://sofirnlight.com/sp31-uv-flashlight-p0151-s0083.html
Is the sale price an actual deal or are there competitors who sell for this sale price as regular price?
Also are there different UV wavelengths and are there reasons to choose one wavelength over another?
FW is junk. Get something with Androol and a side switch.
"Androol"
I like that! 
Yes, UVC and UVB are more useful for rocks, but UVC is exceedingly dangerous as well and should be used with full body protection. I think they usually use full UV spectrum emitters in that case, though.
395nm emitters are crap, mostly visible light
UVC can kill bacteria and mold with a certain varying exposure rate/time, so those are picking up in sales, and probably causing lots of cancer to people who misuse them
What is FW?
The D4V2 is very tempting but i can get two lights for that price and cost is a huge consideration.
Very interesting, thanjs for letting me know.
Is there any safety considerations for the 365nm?
I think he's talking about the Sofirn SP31's firmware, which controls the user interface, which apparently is junk.
Look into the user interface and see if you like it.
There is nothing on the page that indicates how the UI works and the manual page is blank
I am open to alternative suggestions
I don't know UV lights worth a darn, so hopefully someone else will assist you. 
I’m actually a bit…ehhh… in the dark what people use them for? Can someone explain me why I need one?
I live in the desert, and we have scorpions.
UV light makes certain things like scorpions glow really cool.
The sofirn UV is fine, but it does not come with a ZWB filter and you really need to get one. Look on fleabay or somewhere for a 19.5mm or even a 20.5mm (file it down, I just rubbed the edge on concrete until it fit). You can also look for a Convoy S2 or a jaxman mini uv, but
As far as the UI/FW issue, for a UV it isnt that important. You turn it on, you turn it off. There are no low/medium/high/turbo/strobe modes (or shouldnt be) to worry about, so the UI shouldn’t be an issue
As others have mentioned, you want 365nm UVB. You should still avoid looking directly at the beam.
AFAIK there are no legit UVC LED lights available. There are claims of some, and there are “sterilization” products available, but I doubt their efficacy and legitimacy. There are fluorescent bulbs & products available but that’s beyond the scope of this discussion.
Predator-vision.
Interesting.
I have never used Ali Express but have used Fasttech and they have this:
https://www.fasttech.com/products/0/10002364/4021100-convoy-s2-led-flashlight
If you go for a Convoy S2 UV, get this one. I have a few other Nichia UV S2 and this one is more powerful and comes with a ZWB2 filter.
https://www.aliexpress.com/item/32955740360.html
As to what it can be used for… i’d say you’ll find out once you have one. Lots of unexpected things in fact. For instance it lets you spot a lot of stains you can’t see in you’re house - kitchen and bathroom especially. It can be pretty scary actually. Some minerals and woods do fluoresce and shine under UV light. Of course you can check bank notes to see how sophisticated they can be. It is not a light you use much often but it’s good to have one.
There is a very significant oversight here. If you find a good light, like the D4 or D4S, don’t you want more than one? If I love a light, I try and get it in every color. Recently, I have been loving the PD32 v2. Incredible light at $48 with discount.
Yep…
Ok, I’ve ordered The Convoy with the installed filter to check if the lady I pay to clean my house is worth the money…… 
(wonder what she would be thinking if I’d start following her around with the light?)
It’s definitely something new for me so a worthy new addition to my collection.
Btw: over here where I live, it must be about the absolute opposite to a dessert, very few scorpions over here but maybe I can find funny glowing thingies in the water?
I’d love to sell off all my lights and buy replacements.
However my budget is very small. I can afford 1-3 new lights at most.
I actually regret selling the Convoy M1s, in order to buy one replacement costs more than i sold both for.