These pontoon boat corner caps are made of marine grade aluminum. These corner caps are UV Stabilized and are very easy to install. Simply screw them in from the top , a cleat can be added for faster and efficient installation If you purchase our Pontoon Boat F Channel, these are the only corner caps that you can use. Dimensions: 12 inches W X 4 inches H X 3.25 inches D Color: Gray Mounting Hardware not included 0.1875" thick on the sides 0.125" thick up top - **This item is not a 90 degree angle, it is rounded. You may need to trim the edge of your plywood/deck in order for the corner cap to fit properly. **