They are plastic

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Yellow Spring rated -22 to -20 InHg (installed)

hoses or extra assembly is required

and White Spring rated -21 to -19 InHg (installed)

Clutch Kit - Xtreme Performance Heavy Duty Sprung Ceramic 620Nm KMI24001WC-1B JR37 They are plasticXtreme Performance sprung ceramic kit 1B Recommended for: Motorsport ApplicationsThese kits are available with sprung ceramic friction discs and are designed for motorsport applications where higher heat and torque capacity is required. These can also be used in some road applications. Specifications: Torque capacity 620Nm Clamp load Increased over standard Sprung Ceramic Friction Disc Heavy Duty Pressure Plate Kit contains everything you need for a