UTG Model M4/AR15 Handguard Picatinny Rail Set. Designed for Use with M4 Style Handguards . Double Picatinny Rails Allow for Wide Range of Accessory Applications. Tapered Design, Attaches to Handguard with Screws and flare nuts for Quick and Solid Installation. Designed with Swivel Housing and Complete with A Swivel Adaptor to Allow for Additional Optional QD Swivel or Bipod Installation.