watchOS 5.1.1 (build 16R6600) is an official Apple over-the-air update for the Apple Watch Series 4 (44mm, LTE), released on 2018-11-05T18:07:01Z. The update package is 126.69 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: 658638dc9d270a4eb206bf45745b3116568eea00.zip.