iOS 11.2.1 (build 15C153) is an official Apple over-the-air update for the iPhone 6s+, released on 2017-12-13T18:13:58Z. The update package is 315.93 MB. This is a delta (partial) update that requires 11.1.1 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: 699cd4e5bd8efadb2af9a518dacf31cfdafe3e93.zip.