Amazfit T-Rex Ultra 2 / Samsung Galaxy Watch8 Classic (46 mm, Bluetooth)

Sapphire crystal is a cover material that resists scratches better than ordinary glass.

With auto brightness; unavailable in low-temperature mode or below 30% battery.

Thickness excludes heart-rate sensor base.

Health features are for general wellness and fitness, not medical diagnosis.

Separate manufacturer scenarios, not continuous GPS endurance.

Samsung says its charge times were measured with a separately sold 25 W adapter.

Not for technical, cave or mixed-gas diving.

It is sold in one size only.

The rotating bezel lets you scroll lists and apps without touching the screen; its position is read by a 3D Hall sensor found only on the Classic. Quick Button can be assigned to an app or function.

Setup and use need an Android 12 or later phone with more than 1.5 GB of memory and Google Mobile Services.

The second frequency (L5) helps accuracy where signals bounce, such as among tall buildings or under trees.

5ATM suits surface water use such as swimming, not diving or high-speed water sports. Samsung says its MIL-STD-810H testing cycled the watch between –20 °C and 50 °C for 6 hours in total.