Which Check Valves are used for Dosers

[arcos]

I see most Check Valves are for air pumps. Which ones are used for dosers? Also I see some have metal in them.

 

[Shawn Cybulski]

I see most Check Valves are for air pumps. Which ones are used for dosers? Also I see some have metal in them.

Never use them on my Dosers