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More Information for RAYBESTOS MC390121
Professional Grade; New; Bore Size=15/16"

Professional Grade NEW Master Cylinders give technicians a NEW part that fits each application as well as the original. Delivers everything you need to get the job done; lessens installation time and ensures fewer comebacks.


  • Materials and Design Match OE: Vehicle specific designs (cast iron or aluminum); no stress on the brake booster mounting
  • Dependable Operation and Leak-free Performance: 100% pressure tested; meet SAE J1153 and J1154 requirements for reliability and performance
  • All New Parts: New castings, new pistons, new return springs and new components
  • No Assembly Required: Arrives complete and ready to bench bleed and install
  • Geometrically Toleranced: Body and plastic reservoir match center to center for a proper fit and leak-free operation
  • Bore Size and Finish Matches OE: Prevents fluid bypass, which can cause loss of hydraulic pressure; extended service life
  • New Piston Assembly and Return Spring: Prevents brake drag, which can overheat the caliper and rotor; increased pad life
  • EPDM and SBR Rubber Components: Meet SAE specs and are compatible with brake fluid; resist heat, corrosion and leakage
  • Hardened Zinc Dichromate Bleeder Screws: Trivalent coating; extra protection, added durability and longer service life
  • Reduced Warranty Claims: Passes SAE tests for proper function and leak-free operation at hot and cold temperatures
Material Type:Aluminum
Number of Outlets:4
Primary Outlet Size: 
Secondary Outlet Size:None
Alternate/OEM Part Number(s): M390121

Closeout Inventory Warranty Information
Wholesaler Closeout items have a 30 day warranty (but still are covered by our Return Policy).

RAYBESTOS Regular Inventory Warranty Information
RAYBESTOS BRAKES Limited Lifetime: Advanced Technology®, Professional Grade® and Service Grade® Friction Material (Disc Pads and Brake Shoes); Professional Grade Hydraulics (Wheel Cylinders, New Master Cylinders, Brake Hoses, ABS Components, Brake Cables, Brake Hardware, Brake Calipers); Advanced Technology® and Professional Grade® Rotors and Drums. 12 Months: Professional Grade® Hub Bearings. Warranty covers defects in materials and workmanship. Normal/uneven wear is not covered
Warranty Details