watchOS 4.3 (build 15T5209a) is an official Apple over-the-air update for the Apple Watch (42mm), released on 2018-03-12T20:07:05Z. The update package is 133.32 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: f0c6a7e828ed92b9c225c1e0bea399b20e6c11a7.zip.