Compared to a previously bought clone, https://www.fasttech.com/p/1174500, this unit is brighter and has less runtime, with more than 3A measured tailcap current on high with a freshly charged battery. The led is held in place with a tight fit plastic ring over a solid pill; the other clone uses a threaded metal ring, and the pill has a small hole. Both flashlights reach very high led temperatures; using an IR thermometer closely focused over the leds with no lens, I get higher than 110 celsius degrees of temperature deltas, having seen close to 150º of led temperature... Wow! Guess the led won't last very long under such circumstances, buy hey, you can always buy a replacement.

Fully regulated linear driver with extremely low dropout, probably below 50mV in most cases. PWM free. Current adjustable for all regular modes (except strobe). With pleasantly hidden (double click) 12Hz 50% duty cycle strobe mode.

Out of my 5-pack I found large variation in light output between lenses, up to 15% between worst to best and all else being equal. So better grab a much bigger pack than needed so you can ditch the low performers, if you care about this, of course.

Powering up a clock these are already lasting more than other el-cheapo cells. My old "game & watch" units seem to be happy with them also. Great product at a fair price.

I've had these for a good while, with one installed inside a LiitoKala Li-100B charger to read battery voltages. This green leds version works down to 2.4V of input (a smidge below that, in fact). “Calibratable” 😂 using the onboard trimpot. Despite being a 2-wire version, can be easily converted to 3-wire by removing the jumper next to the trimpot and soldering a signal wire next to the red input one.