iOS 11.4 (build 15F5061d) is an official Apple over-the-air update for the iPhone 6s+, released on 2018-05-01T17:06:08Z. The update package is 182.64 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: 072a6b02d2d079e6c7dbcc44ace11eabe6545cea.zip.