In the box there is a warranty card for a 2-year warranty from the manufacturer with a serial number. The sound quality is not as good, but this is normal considering the features of the headphones. As already mentioned at high volume, everything (everyone) is heard, so the drivers will "tickle" your ears. The headphones do not turn off themselves after a long period of inactivity, but I'm not sure if this affects the charge level. For my purposes I'm happy with my purchase.
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