iOS 11.4 (build 15F5077a) is an official Apple over-the-air update for the iPhone 6s, released on 2018-05-14T17:17:19Z. The update package is 276.14 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: f3a599e9821db92921bf4aa57bbd7a7f3a87a350.zip.