watchOS 5.2.1 (build 16U5101c) is an official Apple over-the-air update for the Apple Watch Series 4 (44mm), released on 2019-04-22T17:13:27Z. The update package is 200.84 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: c9bdbc302c1260b505d2300761efe61946a9d398.zip.