The AMAG 21 SG9 is a 21-round SIG P320 9mm handgun magazine that features a stainless-steel body with polymer sub-components. Magpul AMAGs include many of Magpul’s proven features, such as a high-visibility, controlled-tilt follower, stainless-steel spring, flared floorplate that’s easily removable for cleaning and maintenance, paint-pen dot matrix for magazine marking, and capacity-indicator windows that start at five (5) rounds and continue along the spine in one (1)-round increments.