Measure your presser foot from the screw down to the bottom of the presser foot and it will help you determine which shank size.   High Shank: 1-1/4" between top of screw to bottom of presser foot.Low Shank: 3/4" between top of screw to bottom of presser footSuper Low Shank: 1/2" (and under) between top of screw to bottom of presser foot. Please note the super low shank ruler foot will fit most low shank machines. It also has an open top on the shank of the foot making it easier to adjust height-wise.