watchOS 5.2.1 (build 16U5110a) is an official Apple over-the-air update for the Apple Watch Series 3 (38mm, LTE), released on 2019-04-29T17:38:44Z. The update package is 497.26 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: 3d2bc2e9515bc7270611be2b4e2b3b1420d1f5d3.zip.