One pair of 12" X 2" Trailer Electric Brake Assembly Premium OE 12" x 2" electric trailer brake assemblies (1 left + 1 right) for one axle works with most 5,200 - 7,000 lbs trailer axles in the market Center Hole Diameter: 3-1/4", 5 holes mounting, Exchange with Dexter brake # 023-180-00/023-181-00 Only sold by Libra Trailer Parts