Master Series Double Haul replacement Case Clamp and Rack Bracket.The Case Clamp is the part that your Double Haul locks into. The Rack Bracket is the piece that physically connects around your roof rack bars. If you need both parts, choose the button that says both. If you just need one or the other, select the button of the part you need.Order the Case Clamp if you have lost or broken the top flap of the Case Clamp.