iOS 10.3.1 (build 14E304) is an official Apple over-the-air update for the iPhone 6s, released on 2017-04-03T17:00:35Z. The update package is 27.2 MB. This is a delta (partial) update that requires 10.3 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: 242f3df0c318f47aba92a380ed2b51c092fb18d0.zip.