I bought these curtains for the slider leading from my den to 3 season room.  I was a little worried about light getting through with such a light color, but they block the bright, setting sun that comes through the windows.  They also help block coldness coming from the sliders inward.  They are light & cheery, brightening up the room.  I just love these curtains.  You will need to either iron or steam the curtains once out of the package (my picture is before the steaming).