watchOS 5.2.1 (build 16U113) is an official Apple over-the-air update for the Apple Watch Series 4 (44mm, LTE), released on 2019-05-13T17:18:09Z. The update package is 186.72 MB. This is a delta (partial) update that requires 5.2 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: 5b16afd9ce04250fdd1d01dec43048362ab9471d.zip.