The Colt OEM Series offers a no-compromise solution for consumers and dealers to build and offer customized rifles based on the proven Colt M4 Platform. Handguards, Buttstock, Trigger Guard, Magazine, and Rear Sight have been omitted completely. The OEM1 is ready to accept most aftermarket Drop-Instyle Handguards that utilize the factory barrel nut andretaining ring. Also Available with Low Profile Gas Block and without Handguard Retaining Ring