watchOS 5.1 (build 16R5589c) is an official Apple over-the-air update for the Apple Watch Series 4 (44mm), released on 2018-10-22T17:19:59Z. The update package is 59.2 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: ee0b89687a39be92e628b1aae6594c3f47b66a2a.zip.