iOS 12.1.1 (build 16C50) is an official Apple over-the-air update for the iPhone 6s, released on 2018-12-05T18:10:53Z. The update package is 1.29 GB. This is a delta (partial) update that requires 11.3.1 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: 6097cd17f4e1bc27831c41c12b3f62fc1463fc5c.zip.