Radical Firearms RF-15, Semi-automatic, 6.5 Grendel, 20 Stainless Steel Match Barrel, Rifle Length Gas System, Medium Contour Barrel, 1:9 Twist, B5 Stock, B5 Grip, 15 RPR M-LOK Handguard, Pepper Pot Brake, 1 Magazine, 15Rd, Black RF00100 The Radical Firearms 20" Medium Contour 6.5 Grendel AR rifle uses MIL-STD Upper and lower receivers along with their 15" RPR free float rail system for increased accuracy, keeping your hands cool, and giving you plenty of room for accessories. Regardless if it's your first or fiftieth, a Radical Firearms AR rifle will not disappoint!