watchOS 5.2.1 (build 16U113) is an official Apple over-the-air update for the Apple Watch Series 3 (38mm), released on 2019-05-13T17:17:24Z. The update package is 166.52 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: fdf6726e1f9212ef6ac9667568d14874aa0f2764.zip.