HARCO 108-040 4" PVC IPS Gasketed Coupling with Stop, Gasket X Gasket comply with stringent ASTM standards and are NSF-approved for use in potable water systems. Harco Fittings LLC produces a full line of high-strength PVC reducers, tees, adapters, and other specialized fittings for IPS pipe, proven to be the most durable on the market – plus the industry’s simplest and quickest repair coupling. One-piece construction and heavy gasket design assure reliability.