I love this planter box, I ordered 2  48" boxes for a 96" window. I had to put them together, but it was easy and they sent all the parts, as well as a plastic screw tightener. They have holes in the bottom and can hold 6 inch nursery pots, or you can add potting soil and plant, directly. They are very sleek and sturdy. There is no visable space between the two boxes, when leveled and in place. You have to order brackets to mount them under the window sill. I ordered brackets that would a hold 10"  deep box, even though this box is only 7" deep. I didn't want the planter to lean against my brick house and have the plants grow under the protruding window sill. It is easy to move the boxes toward the front of the brackets. Make sure to hang your planter boxes so that the plants have room to grow above the top of the boxes, without blocking the view from inside the house.
They are not self watering.