Zte Blade X8 Quick Start Manual page 10

distance of 10 mm between the unit and the human body. Carry this
device at least 10 mm away from your body to ensure RF exposure level
compliant or lower to the reported level. To support body-worn operation,
choose the belt clips or holsters, which do not contain metallic
components, to maintain a separation of 10 mm between this device and
your body.
RF exposure compliance with any body-worn accessory, which contains
metal, was not tested and certified, and using such body-worn accessory
should be avoided.