After all that time spent poking around the outside, we're ready to start poking at these watches' insides.

Both models open up through the back, same as the Watch3: Four tri-point screws stand in the way, which a specialty driver easily takes care of. Then a quick pry from an Opening Tool gets us inside.

Compared to the relatively integrated rear assembly of the Watch3, the Watch4 offers up a few more bits for early removal: the flex cables themselves, and what seems to be a wire to measure your body composition.

The only silicon we spot here is the Texas Instruments AFE4500S, which handles the optical biosensing.