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 226.02 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: f0f134b928b3bb466545cf1a0b510cab97f9ed91.zip.