My LQS orders this for me and I've used almost 3 bolts. I find it wonderful to use as the backs of quilts I've made for my family members in honor of our Mother. She loved to back her quilts with muslin. But, everyone is correct, you must be picky. Here's what I use and highly recommend:
Roc-Lon -item # 5129 - 200 count -90" wide, 100% cotton muslin - unbleached
Be sure it is the exact # 5129 - other numbers in that brand are quite different.
Then, I use the leftovers to hand embroider/redwork.