watchOS 5.2.1 (build 16U5113a) is an official Apple over-the-air update for the Apple Watch Series 4 (44mm), released on 2019-05-07T17:19:40Z. The update package is 139.58 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: bf04a4cb85b7042ade3f7ec8d8536ca489bbbacb.zip.