I bought JBL headphones and found out they have these holes on both sides. What are they for? They're empty and kinda deep, the headphones aren't wireless so I guess it's not
JBL Tune 510BT | Wireless on-ear headphones
Charging JBL TUNE Headphones Battery (How to TUNE510BT) - YouTube
Amazon.com: JBL Tune 510BT: Wireless On-Ear Headphones with Purebass Sound - Black : Electronics