I'm quite impressed with this fan. For starters, the included battery appears to be is genuinely made by LG and is nominally 2600mAh. I tested its capacity on my Charsoon Antimatter hobby charger. After charging it up to 4.2V, the real discharge capacity was 2550mAh when discharged to 3.0V at 1A. Had I done the discharge in accordance to the datasheet parameters (0.5A to 2.75V) I'm sure it would have exceeded the rated 2600mAh.Now onto the fan. The fan itself is a brushless DC motor - practically identical to a computer fan in terms of construction and noise signature. It's much, much more effective than the cheap brushed motor fans you find for sale everywhere. This fan makes enough airflow to create noticeable cooling even at the lowest setting.Onto the features. The left button turns it off. The right button turns it on. Every time you press the on button, it cycles between modes in this sequence - low, medium, high, sidelight, off. "Sidelight" basically turns off the fan motor and turns on a white LED on the right hand side of the fan (to illuminate the room).There seems to be no way to have the white sidelight and the motor on at the same time. There's also no way to cycle backwards through the modes (eg to go from speed 3 to speed 2). However, after pressing the off button, the next click of the on button always restarts it from low speed. So for example if you want to go from speed 2 to speed 1, you could either press "on" 5 times (to go 3, light, off, 1, 2), or press "off" then "on" twice (to go 1, 2). Hope that's clear, you'll understand immediately if you use the fan. Most competing fans only have the on button, so you have to always go the long way round to decrease speed.It has another cool feature in the form of a blue accent light that illuminates the fan blades. My photo shows what I mean. To turn on that light, you turn on the fan, then hold down the on button for about 4 seconds. This light can only be turned on when the fan motor is operating. It resets to off when you turn off the fan - so you'll have to press and hold the on button again to get the blue light any time you turn off the fan.Lastly, I have to say I'm very impressed with the quality of the instruction book. I'm an engineer by profession and when I get a device like this I normally measure and write down the current draw to calculate the expected battery runtime. In this case the instruction book contains a table of the current, rpm and projected runtime in each mode (see photo). And it's written in good English too.All in all I'd definitely recommend this fan over the half-dozen similar models you'll find for sale for a similar price. The battery alone is worth at least 25% of the value of the whole fan, and the fan is well-built and has the blue and white lights that not many of the competing models seem to have.I can't comment about durability as I've only had it for a few days. However I did a test of the low-voltage cutoff and found that it stops running with a battery input voltage of 3.00V. That's spot-on, it's perfect to prevent over-discharge of the lithium battery, so the fan should give a long service life on the original cell alone. I didn't test the charge cutoff voltage as I use an external fast charger for my 18650s.