watchOS 4.3.1 (build 15T6567) is an official Apple over-the-air update for the Apple Watch Series 3 (38mm, LTE), released on 2018-05-29T17:09:32Z. The update package is 193.18 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: e4ea04ca211db4bf94343bc6f9a73b52d6992e76.zip.