The Midwest Industries customizable rail section kit is designed specifically for the SS-series free float tube handguard. The kit includes one 2.1" rail section and one 4.1" rail section. Constructed of durable aluminum with a matte black finish. The rail is mil-spec 1913 picatinny. Mounting hardware is included. Please note this kit is for the Gen 1 SS-Series handguard and will not fit the Gen 2.