watchOS 5.2.1 (build 16U5091b) is an official Apple over-the-air update for the Apple Watch Series 4 (44mm), released on 2019-04-08T17:13:19Z. The update package is 189.4 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: a57e26bd1886d3078dab66eb53d16a806b7beda1.zip.