Ordinary Swivel: It is made of two parts, a bolt similar to a D-ring and a D-ring, and then the two parts are connected together and a hex nut is welded on it. However, the hex nut is easy to rust and fall off. HAOSAIL Mooring Swivel: It is different from ordinary Swivel in that it is composed of three parts: Two D-rings and a Screw in the middle, the head of the Screw is thickened, the two D-rings are connected with the Screw, and then the D-rings and Screw are welded at the back bottom of it. It is true that the screw's head is not easy to fall off, and the surface is hot dip galv. We can do this production method, is much stronger. If you need any more information about our MOORING SWIVEL parameters, feel free to contact us at: sales@haosailrigging.com