Brake master cylinder leak? Do I need to replace, if so whats the part(02)

Brake master cylinder leak? Do I need to replace, if so whats the part(02)

Image gallery: Master Cylinder Leak

Sinking Brake Pedal - Leaking Master Cylinder Cup Seals Brake master cylinder or booster leaking - Ford Truck Enthusiasts Forums Brake master cylinder leak? Do I need to replace, if so whats the part