Apple Watch — Bands, Bumper Cases & Protection from Series 1 to Ultra 2 (38/40/41/42/44/45/46/49 mm)

Apple engraves the size on the back of the watch (e.g. “45 mm GPS”). Alternatively in the Watch app on iPhone under “General → About → Model”.

Not officially — Series 4-6 (44 mm) and Series 7-9 (45 mm) have different outer dimensions. In practice many 44 mm bands fit with a small gap. For secure hold pick the exact size.

No — Apple Watch SE and SE 2 do NOT have Always-On Display, NO ECG and NO Blood Oxygen sensor. Always-On is from Series 5.

Neither — Apple Watch charges only via the magnetic Apple Watch puck. Series 1-6 with pin puck, Series 7+ with USB-C fast-charge puck.

Ultra (49 mm) has its own ecosystem — Trail Loop, Alpine Loop and Ocean Band. 44/45/46 mm bands from other series do NOT fit — different pin mechanism.