The Phase 5 Low Drag, High Visibility 12 Gauge Shotgun Follower (12GSF) is designed to feed smoothly with no binding in most factory 12-gauge magazine and extension tubes. The 12GSF is precision machined from solid 7075-T6 aluminum bar-stock in the U.S.A. and comes with bright white lettering and a center hole to help verify that the magazine tube is clear by sight and touch.