watchOS 5.2.1 (build 16U5091b) is an official Apple over-the-air update for the Apple Watch Series 4 (44mm), released on 2019-04-08T17:13:14Z. The update package is 462.29 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: 255dea9a564df894a84c5c2f450915c0aa5f55a9.zip.