watchOS 5.2.1 (build 16U5079d) is an official Apple over-the-air update for the Apple Watch Series 4 (44mm), released on 2019-03-28T17:11:37Z. The update package is 440.05 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: f925dcea0c141ca503db1bbfdc13b594cb8bd5f9.zip.