watchOS 5.2.1 (build 16U5110a) is an official Apple over-the-air update for the Apple Watch Series 1 (42mm), released on 2019-04-29T17:38:40Z. The update package is 463.8 MB. This is a delta (partial) update that requires 5.1 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: cc011f24989861b83178a62265a0020ef4107d9d.zip.