watchOS 5.2.1 (build 16U113) is an official Apple over-the-air update for the Apple Watch Series 1 (42mm), released on 2019-05-13T17:16:29Z. The update package is 854.17 MB. This is a delta (partial) update that requires 4.0 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: b90e45161ef5cc01f9856e58be9003e5635cebf6.zip.