This Medallion Deck Bracket is adjustable and is designed for either 2 x 4 or 2 x 6 inch deck rail. Each set of brackets will support approximately 37 lbs. Be sure to use additional brackets for every 18 lbs. of additional weight. These Deck brackets are designed to hold our Galvanized Tapered Window Boxes, Medallion PVC Window Boxes or other similarly sized window box on a 2x4 through 2x6 railing.