watchOS 5.2.1 (build 16U6113) is an official Apple over-the-air update for the Apple Watch Series 4 (44mm), released on 2019-05-13T17:18:00Z. The update package is 73.72 MB. This is a delta (partial) update that requires 5.2.1 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: e25455a1a0fb91014f5e9faf9443765703264c94.zip.