watchOS 5.1.1 (build 16R600) is an official Apple over-the-air update for the Apple Watch Series 3 (42mm, LTE), released on 2018-11-05T18:06:18Z. The update package is 783.4 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: 61b7dc10be1fec4b092e82dba6c76da95f852f2c.zip.