ICON skylight screws are designed to protect your RV. The 20 piece pan head screws come with a rubber O-ring to make a water tight seal when installing your ICON skylight. The screws are also slightly oversized to provide a fresh bite for your new skylight. 18-8 stainless steel, No. 8 size, 1 1/4" long. Use of skylight sealant is still advised underneath the flange and overtop the screw heads. When the skylight is snug tight, back the screw off a quarter turn to provide the skylight some flexibility to shift during temperature changes.