iOS 11.4 (build 15F5079a) is an official Apple over-the-air update for the iPhone 6s, released on 2018-05-17T17:02:30Z. The update package is 42.09 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: 28c87d87472890527b19c9b09d52de0b8cb3ec83.zip.