iOS 11.2.1 (build 15C153) is an official Apple over-the-air update for the iPhone 6, released on 2017-12-13T18:13:07Z. The update package is 1.06 GB. This is a delta (partial) update that requires 10.3.3 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: 5956d33ea592f9a5c97a197b5c9ded78c74983fb.zip.