watchOS 4.3.1 (build 15T5555c) is an official Apple over-the-air update for the Apple Watch Series 2 (38mm), released on 2018-05-01T17:06:37Z. The update package is 326.62 MB. This is a delta (partial) update that requires 4.2.2 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: c7204d283701a6ea43d5e72f1f80e831876a9924.zip.