I have one. It is made of wool. I use it for my self-threading needle when I'm burying knots after quilting or for my needle when I'm doing binding. I like it because I am always setting my needle down or sticking it into something and then forgetting where I put it. Yikes! I'm not sure how I would like a larger one when sewing. I think it would get in the way.
The next thing I'm looking for is a wool wrist one. I would use that style for pins while sewing.