No, it doesn't matter which finger the ring is worn on, but there is some flexibility.

The RingConn Smart Ring can be worn on the index, middle or ring finger of the left or right hand. However, it is important that the ring sits securely and comfortably at the base of the chosen finger. The accuracy of the data depends on factors such as the fit of the ring, finger hair density, vascular distribution, skin thickness and movement artefacts, but not on the specific finger choice.