iOS 11.4 (build 15F5077a) is an official Apple over-the-air update for the iPhone 6s+, released on 2018-05-14T17:17:20Z. The update package is 276.04 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: 9c513116944b3c843813078a65bb5ea8dd33f86c.zip.