watchOS 5.1.3 (build 16S5523a) is an official Apple over-the-air update for the Apple Watch Series 2 (42mm), released on 2018-12-10T18:10:01Z. The update package is 137.59 MB. This is a delta (partial) update that requires 5.1 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: c7ce9205cd285c6ec8a51358bf0d44b0a42efe0d.zip.