iOS 11.4 (build 15F5071a) is an official Apple over-the-air update for the iPhone 6s+, released on 2018-05-07T17:11:50Z. The update package is 276.25 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: 98ea3770d7880ecf2c80eb711f9fc71aeb71c5bb.zip.