[duxup]

Was this a manufacturing issue or something?

How do you manufacture a ring and not know what size it is / sell it to people?

[warp]

to be fair, most smart rings (oura, samsung, even the cheap chinese ones on aliexpress) use ring sizing kits. it seems to be standard practice in this space.

[tadfisher]

Are there different jewelry sizing standards, perhaps?

[jerlam]

Oura Rings (I don't know about the Index) aren't just like other kinds of jewelry. There are protrusions inside the Ring, just like on other wearables like the Apple Watch, for optical sensors that change how it fits. And these smart rings cannot be stretched or modified in any way.