This is single crystal cable with a 4 pin XLR connector and a XLR to 6.35mm stereo headphone plug adapter.
The cable was designed for HE series headphones including HE6, HE5LE, HE4, HE500, HE400 and HE300.
The cable has been included in HE6 accessories.
OCC (single crystal copper) 4pin XLR cable *1 (2 m / 6 ft)
OCC XLR to 6.5mm headphone plug adapter *1 (1m / 3 ft)