This is a strap which connects to your device like mobile phone, PC or something else and gives you a bass / subwoofer feeling which only you feel (not your neighbors) while listening to music or gaming.

Used only a few times since I stopped using headphones. So it looks brand new.
Packaging and everything included.

Current market price for a new item is more than 200€

Some reviews
https://www.nikktech.com/main/articles/peripherals/12089-woojer-strap-edge-haptic-strap-for-games-music-review?showall=1