Gen 2 improvements include nylon tipped tensioning set screw to fine tune the fit of the upper and lower receiver, and an increased magwell flare easier insertion of magazines and a sleeker look. The rear takedown pin detent hole is threaded for a 4-40 set screw. This lower is made in America, machined from 7075-T6 forged aluminum, marked "Cal Multi" with a black anodized finish. It weighs 8.35 oz.