I bought the 1/4 in foot with the guide and loved it, but then I noticed that the guide was slipping off the little bump that held it in place and my quarter in. seam had become wider and wider. I didn't notice it at first so naturally some of my piecing was really affected. I finally realized what was happening when the guide popped off. Since then I have used the etched red line on the same foot and all is going well.