hi Bellaboo,
I'm with Amma, I prefer double folded tape, so I make my own. I use straight grain tape most of the time, only used bias once because I rounded corners of a quilt instead of square corners. You may be confusing "double fold" with binding folded in half and is therefore double. I think double fold tape is where tape are folded toward in and meet at center then it is folded in half. when it is applied you only have single layer of fabric on edge of quilt. I'm assuming that Dodie means that fabric is folded in half (wrong side together) then it is sewed to quilt all raw edges together and then folded edge of tape is turned over edge of quilt and sewed. In this case you have 2 layers of fabric covering edge of quilt. SOMEONE OUT THERE HELP ME ON THIS Also, I think $99 is a little steep to make bias tape which I rarely use.
peel