watchOS 5.1.1 (build 16R6600) is an official Apple over-the-air update for the Apple Watch Series 3 (42mm, LTE), released on 2018-11-05T18:06:24Z. The update package is 174.45 MB. This is a delta (partial) update that requires 5.1 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: 4d884094ae10753d2d924c9d7577cc02fd8a1c57.zip.