watchOS 4.3 (build 15T212) is an official Apple over-the-air update for the Apple Watch Series 3 (38mm, LTE), released on 2018-03-29T17:09:06Z. The update package is 383.99 MB. This is a delta (partial) update that requires 4.1 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: 029f4f68d5e3fb594518b0931abbaac0d13fd758.zip.