iOS 11.4 (build 15F5049c) is an official Apple over-the-air update for the iPhone 6, released on 2018-04-16T17:08:19Z. The update package is 216.25 MB. This is a delta (partial) update that requires 11.4 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: 4bc3d032c6f3613f288da8bf50293655cbf621f6.zip.