Our captive pin d shackles are precison cast with a captive pin. The captive pin is "captured" on the shackle so it is connected to the body at all times. This captive pin makes for easy application and you never have to worry about the pin falling into the water. Our d shackles are made with type 316 stainless steel. Type 316 stainless has an additional element called molybdenum which adds to its durability and corrosion resitant properties as opposed to the more common type 304 stainless.