This is a pair of 12x2 self-adjusting electric trailer brakes for 5,200lb, 6,000lb, and 7,000lb axles. Includes 1 left-hand & 1 right-hand assembly and uses the standard 5-bolt mount backing plate (hardware not included). Fits Dexter, Lippert, Rockwell, AL-KO, and other major axle brands. These are high-quality brakes at a great price!