I think Frixion pens are questionable because of the ink gel reacting with whatever chemicals there are in or on the fabric. I know quilters who think they are wonderful-even Sharon Schambler. I know of one person who shipped a quilt for a contest. The marks came back because the quilt was in the cargo section of a FEDEX airplane. Not a happy event. I like to use children's washable markers on my quilts. They always wash away when I wash the quilt and they never come back.