Find the case size
The case size is engraved on the back of the watch and shown in Settings, General, About. OROBAY bands are made for 49mm, 46mm, 45/44mm and 41/40/38mm bodies.
Match the series
A band with case follows the shape of the watch body, so the series matters: Series 10–12 are slimmer than Series 9 and earlier, and two different watches are called 42mm.
Wrist length
Standard straps fit 6.30–9.06 in, small straps 5.31–7.87 in, long-strap 2-packs 6.97–10.04 in.