watchOS 5.1.1 (build 16R600) is an official Apple over-the-air update for the Apple Watch Series 1 (38mm), released on 2018-11-05T18:05:35Z. The update package is 732.36 MB. This is a delta (partial) update that requires 4.3.1 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: c557cd00575d8b54de46d22c4f3b29ed8e1358f9.zip.