Pump Filter screen?

[HOTTOGO]

I've pulled 4 pumps out now none have had the little filter (screen). I'm putting one together for use w/ lock-up, use a screen leave it out, good thing bad thing HELP?

 

[WE4]

Put it in... what the hell... I leave them out but maybe I shouldnt. I think it is more for that pos 200 solenoid than if you run a 700 solenoid , not a problem. This is not one of the important ones.,....