iOS 11.4 (build 15F5049c) is an official Apple over-the-air update for the iPhone 6s, released on 2018-04-16T17:08:21Z. The update package is 216.45 MB. This is a delta (partial) update that requires 11.4 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: 29da1c92cab257e77d9a253278aec173ea489e1f.zip.