This Icon Technologies set includes 20 stainless steel screws (18/8 steel No. 8, 1 1/4" long) with neoprene gasket washer. Seals to the skylight to help prevent leaks as well as act as an expansion buffer. Use of skylight sealant is still advised underneath the flange and overtop the screwheads. Each screw has an O-ring to prevent leaking for your skylight | Icon Technologies Screws, Qty 20, Natural, w/ Self-Sealing Washer for Skylight Install