iOS 11.2.1 (build 15C153) is an official Apple over-the-air update for the iPhone 6s+, released on 2017-12-13T18:13:59Z. The update package is 316.17 MB. This is a delta (partial) update that requires 11.1 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: b90de17e15d1a3efdcd8e295a34e8d0191980bc6.zip.