Brightent Boat Cover Heavy Duty Water Proof Trailer Fishing Ski Covers (Boat 600D Gray 20'-22' XBT3H) 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.