watchOS 5.1.1 (build 16R600) is an official Apple over-the-air update for the Apple Watch Series 3 (38mm, LTE), released on 2018-11-05T18:05:59Z. The update package is 782.53 MB. This is a delta (partial) update that requires 4.3 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: f254ff423544965336debd056a6d7151f5014a09.zip.