Bomar Commercial Grade Aluminum Inspection Hatch 5-3/16 inch Round Single-Dog Low Profile. Hatch is made of Almag-35 Aluminum and has removable lid for easy access. Locks down with a single t-handle. Non-skid surface. Hatch Opening: 5-3/16 inches (132 millimeters), Outside Deck Flange: 8-3/4 inches (213 millimeters), Cutout: 6-3/8 inches (162 millimeters), Extends below deck: 1/2 inch (13 millimeters), Weight: 3 pounds.