watchOS 5.2.1 (build 16U5101c) is an official Apple over-the-air update for the Apple Watch Series 3 (38mm), released on 2019-04-22T17:13:11Z. The update package is 466.8 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: 3d3e3c7f8636ead1f8675c2bf1ca50a26404d2f7.zip.