This Repair Kit contains a diaphragm of Silicone
 
DESCRIPTION: The N-H420 two-stage regulator is an LPG liquid withdrawal high pressure regulator with a heat exchanger that will vaporize enough fuel for up to 350 HP (261 kW) engines.

OPERATION: With the N-H420's improved vaporization characteristics, liquid propane enters the regulator and then is vaporized using heat from the engine's coolant. Tank pressure is reduced to approximately 1.5 psi (10.342 kPa). As negative pressure is transmitted from the carburetor to the regulator, the regulator releases propane vapor to the carburetor. Some regulators are equipped with a primer button. Correctly installed regulator should not require priming. If priming is required, a maximum duration of only 1 second should be used.