watchOS 5.2.1 (build 16U6113) is an official Apple over-the-air update for the Apple Watch Series 4 (44mm, LTE), released on 2019-05-13T17:18:12Z. The update package is 78.61 MB. This is a delta (partial) update that requires 5.2.1 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: 511b2db70c3f6d2572677ef5f61ea8c1e3c1999d.zip.