watchOS 4.3 (build 15T5212a) is an official Apple over-the-air update for the Apple Watch Series 2 (42mm), released on 2018-03-16T20:09:13Z. The update package is 325.68 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: 57dc04265c46342cb9664c982d562c1c3971c591.zip.