Cast from 356 aluminum alloy, these fittings are designed to handle the demands of big-water boating. We start by machining the shank to match the inside diameter of our aluminum pipe. The saddle, coupled with our stainless steel U-bolt, creates a connection that will hold firmly for a lifetime of boating. LoPro™ includes U-bolts. When custom fitting these to a new pipe, please use a 5/16" drill bit to drill the holes.