MDT's Metal Magazine Extender allows you to increase the capacity of a short action rifle by 2 rounds. It features a lightweight, durable design and can be installed in minutes. This accessory is compatible with metal magazines manufactured by MDT, AICS, and Accurate-Mag AICS that are 3.050" in length. Mag Extender Spring Required. Note: When used with 10 round magazines, a longer spring is required. This extender will not work with any magazine that has any inserts like the MDT 6BR magazine or a metal 223 mag with polymer inserts. MDT Metal Magazine Blk Mag Extender 104373-BLK