This is a shelf with square corners, 36" long and 8" wide as a standard and a polished edge. It is .500" thick. We can make any size shelf that you need so don't hesitate to send us a request. We custom make these every day. If the width is too wide just put in the notes field the exact width that you need as long as it is less in width than 8". If the 36" length is too long just let us know and we will cut it to fit your area perfectly. Please subtract 1/8" from the length as most windows are not square. The thickness of the shelf will depend on how heavy the object are that you wish to place on them. If the total weight is more than what we think the 1/2" will hold then we can make them out of 3/4" but in 95% of the case 1/2" will be fine. We also sell the brackets that will hold your shelves if you need those also. You can see what they look like in the pictures for this product. We include 4 brackets with each shelf, two for the top and bottom of each side. We do this for safety reasons and to save whatever treasures that you will be putting on them from falling into your sink if you happen to put an object too close to the edge and possibly cause the shelf to flip. By putting a bracket on the top edge it locks the shelf in place. We do not include the screws for attachment as there are so many different substrates that are around the windows. If your shelf is wider than your window frame let us know so we can drill the mounting holes in the brackets appropriately.