watchOS 5.2.1 (build 16U5101c) is an official Apple over-the-air update for the Apple Watch Series 4 (44mm), released on 2019-04-22T17:13:28Z. The update package is 132.69 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: 53c5a1d0fd76cebf09d6ca35cecc0e7e2a9f4499.zip.