watchOS 4.3.1 (build 15T5567a) is an official Apple over-the-air update for the Apple Watch Series 2 (42mm), released on 2018-05-14T17:13:53Z. The update package is 326.96 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: 380103d52f9c61ad87e333c46339d6b4090db12b.zip.