Marine fenders are used between marine vessels and docking structures to prevent damage during berthing. They are also used to protect ships during cargo transfers at sea. Marine fenders differ in terms of size, shape, buoyancy, energy absorption, and materials of construction. Cylindrical fenders carry specifications such as length, bore size, and outside diameter. Rectangular fenders may be designed for use with chains and are specified according to base width, height, and chain size. Materials of construction for marine fenders include extruded rubber and ionomer foam. Although rubber bumpers are common, ionomer foam is often chosen because of its environmental resistance. There are many different types of marine fenders. Cone fenders are smaller and less expensive than other products, but feature a high energy-to-reaction ratio. Although cone fenders are used mainly in larger fender-panel systems, they are also used with piles. Cell fenders come in a wide range of sizes and may be equipped with large mounting flanges to help distribute the fender load. Leg or element fenders fit are designed to fit behind a fender panel. They are sometimes used in place of arch fenders, marine fenders that are often chosen for applications in which mounting space is limited. Cylindrical fenders can be attached to docks and other marine structures with chains or brackets. Profile fenders come in cylindrical designs, and as D-shaped, wing-shaped, or square products. Marine fenders that are made of ultra-high molecular weight (UHMW) polyethylene (PE) have a low coefficient of friction and are suitable for applications that do not require energy absorption. Inflatable fenders, extruded fenders, floating fenders, and rubber fenders are also commonly available. In ports and harbors, these marine fenders are used to protect docks, piers, mooring platforms, quays, jetty walls, and marine terminals from tugs and barges. At sea and on inland waterways, boats and ships use vessel fenders. Types of marine fenders include laminated dock fenders, shear fenders, foam fenders, wheel fenders, and buckling column fenders. Laminated rubber fenders are used in barge dock operations and other marine applications that do not require significant energy absorption. Shear-type fenders, as their name suggests, are designed to work in any direction while under compression. Foam-filled fenders feature a closed-cell foam core and urethane covering. Wheel fenders are designed to protect the corners of docks and to provide navigational guidance. Like many other types of marine fenders, buckling column fenders may meet U.S. Coast Guard and U.S. Navy specifications.