Flexible external Bluetooth Wire Antenna with U.FL female connector, 40 mm (1.6 in) length & 0.15 g (0.005 Oz). 

Compatible only with Dronetag BS and Dronetag DRI - variant with External Antenna port. 

Incompatible with Dronetag Mini and Dronetag Beacon due to different connectors (U.FL vs MMCX).