This handguard slides over and is compressed to a standard AR barrel nut, which is not included. If you are replacing a standard plastic handguard and your barrel nut is in good shape, then you are good to go after removing the spring and ring from the nut. Otherwise, order a standard AR barrel nut if you purchase this handguard to replace a handguard using a proprietary nut.
Inside dimensions of 9" battlerail?