watchOS 4.3.1 (build 15T5545b) is an official Apple over-the-air update for the Apple Watch Series 2 (42mm), released on 2018-04-16T17:04:09Z. The update package is 327.54 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: d9823b297731018819ad19fc8acf9f0d70aeaa4f.zip.