iOS 11.3 (build 15E5216a) is an official Apple over-the-air update for the iPhone 6s, released on 2018-03-16T17:05:19Z. The update package is 53.85 MB. This is a delta (partial) update that requires 11.3 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: 3bb8278d3a3470fbee78dd741ad94c45d03d732e.zip.