Speciality designed foot with two slanted grooves through the center of the foot.  This helps to slightly unroll the zipper teeth and for you to stitch as close as you can for the best results.   The transparency of the foot gives better visibility when inserting the zip into the grooves.  IDT cannot be used.
 
Compatible with catagories C, D, E, F, G, J, K
check machine catagory on the pfaff website below
  https://pfaff-australia.com.au/machine-compatibility-chart/