All aboard! Front-side we have:

Bestechnic BES2500YA Bluetooth Audio SoC

A microphone for your voice during calls, which sits next to the opening at the bottom of the headphone stem

And on the back:

The two charging contacts

Another magnet to keep the ear plugs in place when charging

Another microphone for environmental noise cancellation

ThinkPlus Semiconductor SY5500 Battery Charger