Drop-in conversion system replaces the top end of your Glock 20/21 pistol and converts it to fire the hard-hitting, yet controllable, 50 GI cartridge. Developed by Guncrafter, the 50 GI’s head is the same diameter as a .45 ACP, so the rest of your pistol remains stock, allowing easy conversion back to the original caliber. 50 GI ammo can be loaded to drive a 185 grain bullet at 1,200fps, with a felt recoil similar to 230 grain .45 ACP ball ammo. Delivers greater knock-down power, while remaining controllable during rapid fire. Conversion unit comes fully assembled with 4½" stainless steel barrel, firing pin, and guide rod with captive recoil spring. Slide and barrel are precision machined from stainless steel forgings to the same exacting tolerances as the original factory components. Non-reflective, matte finish is durable and good-looking. Black polymer fixed sights with easy to acquire white dot on front sight and U-shaped white outline around rear sight notch. The SF-style magazine uses a modified .45 ACP follower and has an extended base pad that allows it to hold 9 rounds; convenient witness holes at the rear. Fits standard mag pouches for .45 caliber Glock mags. Cut for SF-style magazine catch.