Mach Sakai reviews the Western Arms M4A1 Gas Blobwack PDW which is another variant of the M4A1 GBB from Western Arms that started it all for GBB assault rifles and adapted by several manufacturers for their products. As the review indicates, this is the shortened Personal Defense Weapon variant with the M4 stock rather than the skeletal stock seen at other airsoft retailers and uses the Western Arms "MAGNA" Gas Blowback System.