Heavy-duty 30-gauge PVC Big Bags from Straight Line feature strong, electronically welded seams for ultimate ballast control. One Link valve for clean filling/draining has a weight label around the valve for easy size identification. This spring-loaded Link valve creates a clean, watertight seal that automatically opens and closes when the pump is used for filling and draining, eliminating water sprays into your boat. Color coded graphics provide ideal boat location recommendations. Three 1" standard pipe thread valves for easy custom installation. 38" x 17 diameter.