I love the ones from JoAnn's. They are about 14 x 14 x 4. The 40% off 13.99 (more for colors) makes them affordable at $8.40. They are big enough to hold all the fabric (except backing & sometimes that too) for a complete lap project & the finished blocks. Great for travel because of the handles. The fabric & blocks do slide to the end if you hold by the handle. They, also, stack very nicely. I haven't tried the ones from Michael's or Hobby Lobby so can't comment on them. Wal Mart has some good ones, but most don't have handles, or are too deep. I have used some of the shallow ones for holding the project, but move to the JoAnn boxes when I start sewing.
http://www.joann.com/artbin-super-sa...2-6E75F2A5E1BC