Lifetime fiber reinforced diaphragm made from fluorosilicone. Silicone can deal with the occasional diluted chemicals, but it will melt and dissolve under anything else. Silicone rubber is not meant for automotive applications as it would be constantly exposed to brake fluids and petroleum oils. In contrast, fluorosilicone rubber distinguishes itself based on its unique properties. It will withstand almost every chemical out there with the expectation of a select few.

This listing includes:
PCV Valve diaphragm cap
Diaphragm for check valve on the bottom of the housing
Spring and retainer