watchOS 4.3.1 (build 15T6567) is an official Apple over-the-air update for the Apple Watch Series 3 (38mm, LTE), released on 2018-05-29T17:09:33Z. The update package is 151.58 MB. This is a delta (partial) update that requires 4.3 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: c2da5511d8f4383f79a44c989daff01a7576fd86.zip.