It's a head band which is for wireless microphones BeyerDynamic S85 series (HF), S185 (VHF) and S700 (UFH).
Head as well as for the singing to the sound.
I use it for years. His only complaint and weight, and perhaps look a bit outdated. But it is an unstoppable header.
Of all the wireless microphones (pro) I've tested, this is probably the one that offers the best timbre, greater respect for the original.
Ideal for its distinctive, gospel music genre, see outright plugs sound when the cable length is an obstacle. The quality of issuers Beyer does the rest.