ATE Master Cylinder Booster O-Ring for Porsche 911/924/928/930/944/968 (1974–1995)

This ATE master cylinder booster o-ring is a direct-fit replacement for Porsche applications listed in the fitment table below. ATE, a division of Continental AG, has been engineering hydraulic brake systems in Germany for over a century. An OEM supplier to manufacturers like Porsche AG, Mercedes-Benz, and Volvo, ATE produces factory-level rotors, pads, and hydraulic components built to strict European standards. Known for consistent pedal feel, proper fitment, and long service life, ATE remains a trusted choice for reliable, OE-quality braking performance.

Technical Details

• Manufacturer part number: 390479
• Function: Seals the master cylinder to the brake booster to prevent vacuum leaks
• OE cross-reference: 251 611 243

Fitment & Compatibility

Use the fitment table below to confirm year/submodel and to catch any option notes. If you’re unsure about fitment or left/right, send us your VIN and we’ll help you verify it before you order.

We’ve been doing Porsche brake work for over 20 years, and we still treat fitment questions like they matter—because they do.