watchOS 5.2.1 (build 16U5113a) is an official Apple over-the-air update for the Apple Watch Series 4 (44mm), released on 2019-05-07T17:19:41Z. The update package is 136.25 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: e61ff4338f72f22351c0092604d2352d3bc154e1.zip.