Made of nylon, excellent corrosion resistance from seawater and , withstands salt air on the boat Nylon is a more and less expensive solution, the strength and lifespan are exactly the same as 316 stainless steel Used for splash-proof openings or exterior venting of wiring cables, wires, pipes SMOOTH: The flush screw covers the contact area smooth and nice. The edge of is smooth and thick SIZE: about 2.5 inch x 2-1/4 inch, height: 1 inch color: black Material: nylon Package Contents: 12 x Cable Vent Cover (with screws) Only the above package content, other products are not included. Note: Light reflection and different displays may cause the color of the item in a little different from the real thing. The measurement allowed error is +/- 1-3 cm.