watchOS 4.3 (build 15T5212a) is an official Apple over-the-air update for the Apple Watch (42mm), released on 2018-03-16T20:09:02Z. The update package is 133.34 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: 00b6309244bae362bafd7425498b6e6e9731b0b2.zip.