Thru-hulls are made with a durable, thermoplastic construction which prevents electrolysis. The Thru-Hull Connector fits 1 1/2 inch Hose size. The stem length is 3 1/2 inches. Maximum hull thickness for the Thru-Hull Connector is 1 1/4 inch. The flange diameter for the Thru-Hull Connector is 3 inches. Installation hole size required for the Thru-Hull Connector is 3 7/8 inches to 2 inches. The Thru-Hull Connector is constructed of polypropylene and is backed by Attwood 1 year warranty. Caution: Thru-Hull connectors are designed for installation above the water line only. To place an inquiry phone: (616) 897-2290 between 8:00 a.m. And 5:00 p.m. Est fax: (616) 897-8358.