For large or jumbo piping the adjustable foot is ideal.
 
Suitable to put in zips, especially zips with larger teeth that may not pass through the standard clip on zipper foot.
 
A screw on type foot which can be adjusted so the needle will sits close to piping or zips. Can also be adjusted for straight stitch sewing with a centre position in the foot.
 
Also useful for topstitching close to the edge, line the side of the foot up with the edge, but have the foot adjusted so the needle is in the centre position and your stitched will be a small distance away from the edge.
 
NB - Not available for category D models