watchOS 5.2.1 (build 16U5079d) is an official Apple over-the-air update for the Apple Watch Series 3 (38mm, LTE), released on 2019-03-28T17:11:09Z. The update package is 180.54 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: 8d460a2b1092a9787478a7a6868d3a6a8e0b5475.zip.