Bought today two Sigelei 30 W mini. I tought that the ability to swap the 18650 in a flash is very important. Last week I had the Sx mini, wonderful piece of hardware (but I don't lime the menu), just too expensive to daily vape, since I treat my e-cigs just like my pens... they falls a lot, from the table, from the hands, you imagine. So the Sigelei 30W seemed to fit the bill. I had no QC issue; just maybe the display, which is tilted one degree in one of the two devices. Paid 35 British pounds shipped. I was to decide between the MVP 30 Watts, the eLeaf 30 Watts and the Sigelei 30 Watts; the Sigelei, at least on paper, was the best one. The MVP 30 W has that odd recharging cable and departed from pure DC drive; I was done by four 20W eLeaf that I had to retire early because of the soft 510 thread and Mean value display. So the Sigelei looked best. As soon I placed the battery inside the real problem become obvious: the display indicates (on both of them) about 25% more of the power really delivered to the atomiser. This confirmed scientifically later when I connected a lab power supply instead of the 18650 and made a power measurement. I like the Sigelei boxy shape, it is very good otherwise, if you except the soft 510 thread a-la-eLeaf. Also, I would have liked a stainless steel 510-to-eGo adapter instead of the gummy outer skin.
Basically, the Sigelei mini is a 20 Watt (well, 21 or 22 with a fresh battery) device sold as a 30 Watts. Please note I were correctly on PWM mode, not DC-DC mode.
Chinese discounted watts? I don't think it is a QC problem, as the two Sigelei mod boxes I have shows this unflattering "feature". I should have waited for an informed review before buying, as the ones available at this time are all impressions and opinions (and smoke).