watchOS 5.2.1 (build 16U113) is an official Apple over-the-air update for the Apple Watch Series 1 (38mm), released on 2019-05-13T17:16:14Z. The update package is 449.77 MB. This is a delta (partial) update that requires 5.1.2 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: 5d64dd6a54a7744bdaf85b433acb045f99361d53.zip.