Pellon 830 Easy Pattern -- like a very thin interfacing, flexible but doesn't shrink or stretch. Comes on the bolt 42" wide (yes, 42 not 21 like clothing interfacing). I think it has gone up to $2.49 a yard, but with a 40% coupon from that big box store .... I think it is sold as a material if you are drafting a pattern, or making a new one from one used too often and is falling apart. I love it for string projects.