This all 18-8 stainless steel mount attaches to any vertical flat surface such as bulkheads, hulls, transoms or cabin sides. Also mounts to square and flat rails. Fits HORIZONTAL RAILS up to 2-1/4 in. (57.2 mm) high by any depth or VERTICAL RAILS up to 1-5/8 in. (41.3 mm) wide by any depth. Some fasteners required for installation.