Stern def.Magazine adapter ad9 s&w m&p/sig p320 9/40 mags FEATURES:Made in the U.S.A.Constructed from 6061 T6 aircraft grade aluminum4140 NiB coated feed rampHard coat anodized type 3Sturdy ConstructionErgonomic mag releaseWorks with all generations of M&P magazinesWorks with P320 and P250 magazinesWorks with any mil spec ar15 lower receiverAll gun components besides the Bolt and Barrel remain stock Other Features: Must be used with a 5.4 ounce buffer or heavier when using a carbine spring.Buffer not included.Allows standard mil-spec ar-15 lowers to accept 9mm and 40s&w s&w m&p series and sig p320/p250 magazines, requires a glock cut bolt