Quilt store fabric is top grade# 1 fabrics this means there is less than 3 blimishes (weavers knots,start-stop marks,split picks,double picks, ect.) per 15 yards. which is what quilt shops usually order. There is no difference in the tightness or how loose the weave is on the same frame. The looms that make the fabric has a beam that holds the thread or warp threads(lenght)and will not run if it is loose on either end.But some looms will run loose, but from beginning to end.Fabric is graded by number of threads per sq. inch.many companies made cheaper fabric to start with, and more bad places and sell at a lesser price.