watchOS 4.3.1 (build 15T5545b) is an official Apple over-the-air update for the Apple Watch Series 2 (38mm), released on 2018-04-16T17:04:04Z. The update package is 327.51 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: f119e66c7762605b3853bdedf58ed37c2b4ca577.zip.