watchOS 5.1.1 (build 16R600) is an official Apple over-the-air update for the Apple Watch Series 1 (38mm), released on 2018-11-05T18:05:34Z. The update package is 965.85 MB. This is a delta (partial) update that requires 3.1.3 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: cd63c9c6260d8822fc304adbff2f3613cbaf1945.zip.