These feet are for sewing close to any zipper, buckle or any other area where sewing close to the edge of the foot is needed.  This two piece set comes together with an inner and outer presser foot.  These feet are used for any unison feed or compound feed walking foot machine.  This includes the TN-650BL, TN-750BL, TN-1541, TN1508 and 1510 flat bed machines as well as the TN-246A and TN-1341 machines. 

Zipper on the left, foot on the right = right foot