watchOS 4.3.1 (build 15T6567) is an official Apple over-the-air update for the Apple Watch Series 3 (38mm, LTE), released on 2018-05-29T17:09:35Z. The update package is 73.95 MB. This is a delta (partial) update that requires 4.3.1 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: 4f0e4a9cdbdfde3a1026cd2323252d3bda65050d.zip.