Our New Vented Stone Krusher Flat Spiked extension for the MPA 9mm Mid Sized with 3/4x10 Threads offers a new design and length. For door breach, defense and barrel counterbalance. This machined aluminum vented extension is finished in flat black anodize, 7 inches in length and weighs about 14 ounces. Threaded in 3/4x10. *Will Not fit 930 / Mini.