The original, Steam-A-Seam Sticky Back, has the pressure sensitive adhesive (the "stick") on one side which allows for a temporary hold to the appliqué material. It shifts easily on the second material allowing you to quickly reposition your appliqué pieces until pressed with an iron for a permanent bond. Once fused the bond is the same as Steam-A-Seam 2. Sold by the half yard unit, 12" wide. 25 yards per bolt.