watchOS 5.2.1 (build 16U5110a) is an official Apple over-the-air update for the Apple Watch Series 4 (44mm, LTE), released on 2019-04-29T17:39:55Z. The update package is 472.93 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: a389587c77dfb660a429e6e01f82f491c5eddff7.zip.