watchOS 5.2.1 (build 16U113) is an official Apple over-the-air update for the Apple Watch Series 4 (44mm), released on 2019-05-13T17:17:57Z. The update package is 453.68 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: 6d061ac18ca79d9c698dad91d18cf2eaeefbda00.zip.