watchOS 4.2 (build 15S5102b) is an official Apple over-the-air update for the Apple Watch Series 3 (42mm, LTE), released on 2017-11-17T18:17:58Z. The update package is 1.58 GB. This is a full OTA update that can be applied from any compatible base version. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: 6b49762848d952ecd539e0d852d5ba9634373f22.zip.