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 HE-6, HE-5LE, HE-4, HE-500, HE-400 and HE-300.
The cable has been included in HE-6 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)