These bases are made from 6061 Alum. They are designed to screw to the inside wall of your boat or fit in the inside track system on your boat. Can be purchase with 3/8- or 1/2-inch threads. They are 3/4 x 1-1/2 x 2-inch rectangle shaped. Purchase all you need and ship for $15.00

                                     Proudly Made in the USA