watchOS 4.3 (build 15T5199f) is an official Apple over-the-air update for the Apple Watch Series 2 (42mm), released on 2018-03-06T18:08:07Z. The update package is 325.75 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: 53880013785692bde1b728c4555802f8e4ce5052.zip.