QUALITY-BUILT Premium brake master cylinders are engineered to restore factory brake responsiveness and deliver consistent hydraulic pressure-whether you're navigating city streets or cruising the highway. Ideal for vehicles needing a dependable OE-style replacement, they offer a direct-fit solution to maintain braking integrity. Each unit is manufactured to precise OEM standards using high-quality castings and seals for reliable fluid control, leak resistance, and extended service life. The result? Confident pedal feel, accurate pressure modulation, and smooth, predictable stops in every condition. QUALITY-BUILT Premium master cylinders undergo 100% pressure testing and include factory-style reservoirs where applicable, ensuring proper fluid capacity and fitment right out of the box. Internal components are engineered for durability and consistent output-mile after mile. Designed for easy installation and long-term reliability, QUALITY-BUILT Premium master cylinders are trusted by DIYers and professionals alike. Pair them with QUALITY-BUILT brake components for a complete brake system refresh-built for durability, engineered for peace of mind.PART SPECS: DESC: QUALITY-BUILT Premium Brake Master Cylinder NM55447 - Compatible with 2004-2019 BMW (525i,525xi,528i,528i xDrive,528xi,530i,530xi,535d,535d xDrive,535i,535i GT,535i GT xDrive,535i xDrive,535xi,545i) Master Cylinder Bore Diameter inches: 1.063