iOS 12.1.1 (build 16C50) is an official Apple over-the-air update for the iPhone 6s+, released on 2018-12-05T18:10:59Z. The update package is 1.42 GB. This is a delta (partial) update that requires 11.1.2 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: 9d3b8ac951a7a467ca3b4a9c85f82bad7c07214c.zip.