LBE Unlimited Mil-Spec Diameter Buffer Tube, 6 Position, Fits AR-15, Black MBUF002 The Six Position LBE Mil-Spec Spec Diameter Buffer Tube fits all collapsible AR-15 stocks that require mil-spec tubes. This item is perfect for your current build or your spare parts bin. LBE Unlimited is a leading producer of US Made gun parts and accessories.