How important are these seals?

[Banshee2105]

I just got finished with putting my top end together and realized that I didn't put in the bottom cylinder seals pictured. How important are they? I have base gaskets on there that should stop any coolant from flowing in unwanted places. If you guys say so though, I'll pull it apart and put it back together. Part number 6 in the schematic below. Thanks!

 

 

Part number 6 in this schematic:

[camp0429]

It will leak without them. I've had to change them out because they leaked

[locogato11283]

Those are a must.

[trickedcarbine]

Need