X-CALIBER Survival-Rifle Gauge Adapter System - Soldier Systems Daily
Caliber conversion sleeve - Wikipedia
SHOT Show 2015: Chiappa X-Caliber Survival Rifle/Shotgun - The Truth About Guns
SHOT Show 2015: Chiappa X-Caliber Survival Rifle/Shotgun - The Truth About Guns
Eagle Gun Range -Macon GA - X-Caliber Ammo Adapter Set for Shotguns. It's an 8-piece set of drop-in adapters that measure seven inches long each, and it comes with a carrying case.
The Utility of 12-Gauge Caliber Adapters, The Good, Bad, & Ugly -The Firearm Blog