w116 300sd Vacuum Check Valves

[xaliscomex]

1979 300sd

Have 3 check valves left in my garage that were purchased more than 10 years ago.

I recently replaced a check valve on my w116 300sd and that fixed the problem with my diesel not shutting off.

I went online to search for check valves and I got prices that vary.

Some check valves indicate that they are 2 way and others don't indicate anything but the manufactures name.

Who makes the best check valves and which manufactures should I stay away from?

Do all blue/black check valves function the same?

Please advise