The Graco 117828 manifold filter o-ring creates a seal between the threaded filter cap and O-ring that goes inside the filter cap and surrounds the manifold filter. Typically this needs to be replaced when paint is leaking from the sprayer through the manifold cap.
For use with these airless sprayers:
Part #: 115099
Part #: 246384
Part #: 117559
Part #: 103413
Part #: 287167