watchOS 5.2.1 (build 16U113) is an official Apple over-the-air update for the Apple Watch Series 1 (38mm), released on 2019-05-13T17:16:17Z. The update package is 449.95 MB. This is a delta (partial) update that requires 5.1.3 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: 92eb450624f142a00137cdc0924fbad6d43a871f.zip.