Which shader to chose when you want clean horiz. scanlines only?

[ArcadeTV]

Hey Guys, thank you for all your hard work, I just got into RPi and recalbox, I'm really having fun!
So, I'd like to ask -
It looks like all shaders that add scanlines to the video also add a certain amount of vertical lines to the output image...
is there a shader that only adds horizontal scanlines and nothing else?

Thanks again,
-Alex-