SPECTRUM
Unlike broad-spectrum fluorescent tanning lamps or mercury vapor UV lamps, UV LED flashlights are very specific. Their wavelength varies by only by ±5nm. If they are 365nm, the only put out 360nm - 370nm (NOT 385nm). If they are 395nm, they only put out 390nm - 400nm, (NOT 385nm). If they are 405nm, they only put out 400nm - 410nm (NOT 385)
SOLAREZ resins require 385nm to cure properly. If you use a 365nm flashlight or a 395nm or a 405nm, you may get a tacky surface cure or perhaps inadequate adhesion to the base or sometimes a liquid vacuole may appear. All aberrations associated with improper lighting
INTENSITY
The old-style "bulb-like" LEDs from the 1980's or '90's are obsolete compared to today's SMD (sheet mounted diodes) style chips. They GREATLY exceed the bulb-style lights output, no matter how many of them you have i.e. you can have a bulb-style LED flashlight that has 64 bulbs and still not have nearly the intensity as a single SMD LED.
BATTERIES
SOLAREZ UV flashlights choose to use "Button-Top" Lithium Ion 18650 batteries because they have long-lasting power for thousands of short bursts and are rechargeable many times. There are "flat-Top" 18650 batteries designed for "vaping" machines but these are designed for high-intensity discharges for the vaping needs. Don't use these in Solarez flashlights. Also, don't use two CR-123 batteries in series. The voltage is too high.