iOS 11.4 (build 15F79) is an official Apple over-the-air update for the iPhone 6s, released on 2018-05-29T17:16:27Z. The update package is 1.3 GB. This is a delta (partial) update that requires 10.3.3 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: dfa09fab40edcd9e6f896715ae1b0f9300f0238a.zip.