iOS 11.4 (build 15F5037c) is an official Apple over-the-air update for the iPhone 6, released on 2018-04-02T17:06:56Z. The update package is 261.02 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: 2c6029b8ff080653d2d7aaca6bcd7b3c65a804e3.zip.