Here are a couple of posts that they talked about them
http://www.quiltingboard.com/posts/list/8591.page
http://www.quiltingboard.com/posts/list/15/6587.page
http://www.quiltingboard.com/posts/list/4396.page
http://www.quiltingboard.com/posts/list/5598.page
there are more but this will get you started