All together, this back cover is home to a tiny speaker and linear actuator, a microphone, a barometric sensor, and the heart rate and SpO2 sensors. Most of those parts live on the same flex cable octopus, which is not removable.

The only replaceable part in the bunch is the loudspeaker—if you trust the reading on the other side of the "not removable" battery. Which... we don't. It seemed perfectly removable to us!

The power cell delivers 1.59 Wh (410 mAh @ 3.87 V). That puts it above the Galaxy Watch3 (1.3 Wh) and the Apple Watch Series 6 44 mm (1.17 Wh). Only the Xiaomi Mi Watch from 2021 provides more juice with 1.62 Wh.