This Moro Kaiser 5" Tank Sight Glass Assembly comes with a neoprene o-ring, a heavy-duty lens, and a steel weldable base. The Moro Kaiser sight glasses are constructed with endurance in mind by using heavy-duty steel to craft the base of the sight glass assembly, a tempered glass lens, and a neoprene gasket to ensure a leakproof seal. The durability of this sight glass makes it great for initial purchase or replacement.