This stainless steel "V" bracket is designed to fit over most any kayak's stern as the bracket can be bent to fit the shape of the hull. SeaLect also makes two other brackets for mounting to square stern kayaks.  If you are building your own kayak and are attaching a rudder, you can either purchase the "V" style or cut off the end of your kayak for square stern.  If you wish more info and pricing on the square mount, e-mail us and we will gladly get back to you.  It is not an item we stock.