iOS 11.4 (build 15F5077a) is an official Apple over-the-air update for the iPhone 6, released on 2018-05-14T17:17:18Z. The update package is 275.8 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: 0231572c469b985cd66070afed88e343de0c5b23.zip.