Tie Down's Hydraulic Trailer Drum Brakes are the most corrosion-resistant free-backing drum brakes on the market. The brakes' Galv-X coating is composed of inorganic polymers which bond metallic zinc flakes to the metal surface. Designed with aluminum wheel cylinder and stainless steel springs for superior saltwater performance. The drum brake kit comes with brake shoes and mounting bolts. Trailer drum brake hub sold separately.