watchOS 5.2.1 (build 16U113) is an official Apple over-the-air update for the Apple Watch Series 4 (44mm, LTE), released on 2019-05-13T17:18:07Z. The update package is 473.54 MB. This is a delta (partial) update that requires 5.1.3 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: d4497e4ee9dbfb65241d11f7e2777c7c980e7dc8.zip.