The Colt M4 Carbine OEM1 is a customizable rifle based on the proven Colt M4 platform. It offers a no-compromise solution for building personalized rifles. This rifle is ready to accept most aftermarket drop-in style handguards that utilize the factory barrel nut and retaining ring. It is also available with a low profile gas block and without a handguard retaining ring. Please note that there are restrictions on the sale and ownership of this product in certain states.