US Filter RO-2127, RO-2300, RO-2300-A, RO-3167 Replacement O'ring US Filter RO-2127, RO-2300, RO-2300-A, RO-3167 Replacement O'ring fits models: RO-2127, RO-2300, RO-2300-A, RO-3167 Replace your O-Ring with every 3rd filter change to prevent leaks 3 5/8 inches (outside diameter) Quality Replacement parts by TORK