I didn't use these right away because I was busy with other things, but then I remembered them and took them out of the box.  I was immediately struck by the brightness of them and was concerned that the weight of them was too light to afford any room darkening properties.  So after hanging them this is what I want to say.  I was happy with the lite-weight material; they don't darken the room like I thought BUT they do keep a lot of heat out which was our major issue.  I was surprised how much I enjoyed having them in a sunny window because I still get my sun but not that heat!