watchOS 4.2 (build 15S5085b) is an official Apple over-the-air update for the Apple Watch Series 3 (38mm, LTE), released on 2017-10-30T22:07:32Z. The update package is 218.44 MB. This is a delta (partial) update that requires 4.0.1 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: f78f7691638c7cda8aa1e16d5548ba534dbb777f.zip.