There are different qualities of most fabrics. The lesser grades of flannels will be thinner, the print might not be even or printed crooked. Some fleece will pill after the first time thru the wash. Others not at all ever. I have at least 2 brands of solid black quilting fabric in my stash right now and they are both different when you compare them next to each other. One is much thinner and almost see thru vs the other one. Just look carefully at what you are buying before you get it. Personally, I've only used flannel to make PJ pants.