I bought two of these bags to use for carrying spindles. They're lightweight and just the right size to carry a nice bit of fiber and a top whorl spindle. The silk fabric is slick enough that the fiber easily slides in and out. It was extra nice that I found them on sale!
However, my dpn's stab through the fabric with ease and I thought there would be some kind of thing to stop the yarn ball from pulling out. Seems like a reasonable and practical thing to me. Instead, I used a safety pin so the yarn stays in the bag. It is the perfect size to hold a sock project on the go.