Sierra 18-4265 Pipe PlugSierra replacement pipe plug for Mercury and Mercruiser engines. Thread Size: 3/4" or 19.1mm - 14 NPT; Material: Brass; Interchangeable with: GLM; 21896; Mercruiser Stern Drive; 22-42681; 22-426811; 22-428611; 22-861187; 22-8M0204679; Mercury Marine; 22-428611;