watchOS 5.1.1 (build 16R600) is an official Apple over-the-air update for the Apple Watch Series 4 (44mm), released on 2018-11-05T18:06:52Z. The update package is 159.26 MB. This is a delta (partial) update that requires 5.0 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: f2c0b4232a21c901dabacedf4fb0b7519435d974.zip.