The TTI 4mm magazine basepad extension is a mid-profile solution designed for 2011-style 9mm/38 Super magazines. This gray hard coat anodized extension increases capacity by +2 rounds while maintaining USPSA compliance.TTI 2011 Magazine Extension - 4mm ProfileCompatible with Staccato Infinity Springfield Prodigy Atlas brands+2 round capacity increase (20 to 22 rounds)Works with factory spring and followerRecommended for 140mm magazinesFits USPSA 140mm gaugeGray hard coat anodized finishIdeal for competitive shooters and enthusiasts seeking increased magazine capacity while maintaining reliability and USPSA compliance for their 2011-platform pistols.