i have one of them.
the Battery is double of the original thickness,
by charging it dosnt heat but it need the double time for charging,
the lifttime with one charging feels about double then the orginal
and if you look at the production details there is witten "Stable and safety with circuit protection" and i think its truh
the battery cover fits OK but only on top its about 0.15mm to big.
i use them for wifi hotspot in park or by travel
the delivery from the ebay seller is about 1,5weeks from HongKong to germany