watchOS 4.3 (build 15T5176c) is an official Apple over-the-air update for the Apple Watch Series 3 (42mm, LTE), released on 2018-02-07T18:10:15Z. The update package is 353.47 MB. This is a delta (partial) update that requires 4.2 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: 1edb2b61f3c367a6e822dd5c86ab9d2369f07400.zip.