The even feed foot has a set of teeth to work in conjuction with your feed teeth on the machine.  It will sandwich all your fabric layers together to evenly pull them all through at the same time.  Perfect for quilting straight lines or any other tricky to sew fabric.  This foot will help with stretch fabric, to help illiminate the stretch as it is sewn
 
7mm low shank screw on foot.  Suitable forsuitable for 7mm machines MW, DC, skyline S3, jem, memory craft 6600p, 6500p, 5200, 4900, 3500, sewist, MS