Brightent Boat Cover Heavy Duty 600D 17' 18' 19' Water Proof Trailer Fishing Ski Covers XBT2H This item is made by 600D woven polyester material with PU coating, MARINE GRADE, which is very good water-proof. Our cover has a 18 meter extra belt, you can use it to tight from the front to rear of the boat. This can provide extra secure of the cover.