Sierra 18-4258 MerCruiser Pipe PlugSierra stainless steel pipe plug with square drive. Note: Pipe sealant with Teflon is recommended for use on plug threads. Thread Size: 3/4" - 14 NPT; Use With: 18-1949 Manifold Spacer; 18-1984 Manifold Spacer; 56507 Loctite Pipe Sealant; Interchangeable with: Crusader; 113186; GLM; 21892; Mallory; 9-41205; Mercruiser Stern Drive; 22-33198A1; 22-41622; 22-46754; 22-33198; Osco; 1016012;