Style A-external hinge. Anodized heavy-duty aluminum frames. 1-1/2" height above deck. Extra high sealing lip on base. Heavy-duty acrylic top and heavy-duty hinges. No sharp corners to snag lines or sails. Quick acting, adjustable tie down dogs. Locked vent position. Cut Out 20-1/4" x 20-1/4" Flange 22" OD x 22" OD