F M&P 9/40 MAG EXTENSION GRY $34.80 MESW-5/4GR show more like this Calculated in Cart DACK Outdoors F M&P 9/40 MAG EXTENSION GRY MAP MESW-5/4GR show more like this Calculated in cart GunZoneDeals F Warne S&W MP 9/40 Magazine Extension MESW-5/4GR $35.99 MESW-5/4GR show more like this Sahuarita Guns F Warne Magazine Extension Fits S&W M&P 9/40 - +5/4 - Gray $39.00 MESW-5/4GR show more like this Calculated in Cart Primary Arms F M&P 9/40 MAG EXTENSION GRY MAP MESW-5/4GR show more like this Free shipping over $400 (Excludes Ammo) Gman Sport F Warne M&P 9/40 Mag Extension Gry MESW-5/4GR MAP MESW-5/4GR show more like this Firearms $18.45, Free over $500 Shooting Surplus