This is the one for my machine:
https://www.husqvarnaviking.com/en-U...oidery-Foot,-R
I also use the Fine Line Clarity ruler foot, especially when I'm doing a combination of ruler and freehand work.
https://www.sewingpartsonline.com/fi...ler-foot.aspx?
If you're getting lashing when using the ruler foot, you likely need to adjust the height of the foot - even half a millimetre higher or lower can affect stitch quality. (You would likely need to lower it)