watchOS 5.1.3 (build 16S535) is an official Apple over-the-air update for the Apple Watch Series 2 (42mm), released on 2019-01-22T18:11:05Z. The update package is 171.57 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: 1186f28ba9d7912a73275c58b6da07ee2612fc18.zip.