watchOS 4.3.1 (build 15T5535b) is an official Apple over-the-air update for the Apple Watch Series 2 (42mm), released on 2018-04-02T17:13:13Z. The update package is 327.55 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: 37417d0be26bc0e09f3ebe750ed2a6bea9adda55.zip.