watchOS 5.1.1 (build 16R600) is an official Apple over-the-air update for the Apple Watch Series 1 (42mm), released on 2018-11-05T18:05:46Z. The update package is 962.01 MB. This is a delta (partial) update that requires 3.2.3 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: 57ff9620a061d8b8a9d678dae6e36ea302f2fb5e.zip.