iOS 12.1.1 (build 16C50) is an official Apple over-the-air update for the iPhone 6s, released on 2018-12-05T18:10:52Z. The update package is 1.33 GB. This is a delta (partial) update that requires 11.2.5 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: 71eb907b9c36653c63035c2c0ecb92ae4258b21d.zip.