I did contact them recently and they stated that they use standard National pipe threads. So if correct it is very likely that threads on the needle valve are 10-32. Does the needle valve screw right into manifold(Solenoid) or is there a adapter. If a adapter the threads on the manifold are likely 1/8" NPT, and the adapter converts from 1/8" NPT to 10-32. Or they could be 1/4" NPT, you could confirm that if the fitting appears the same size as the main inlet nipple as the industry standard is a 1/4" NPT nipple. But I suspect the needle valve is more likely a 10-32 thread that connects to the manifold directly or if it uses a adapter than it's a 10-32 thread to a 1/8" NPT adapter into the manifold.