These versatile, straight-sided rubber test plugs can be used to block off almost any easily accessible opening. They feature durable brass hardware, solid rubber, and a corrosion-free wingnut. Our large, heavy-duty plastic wingnuts are about the same strength as brass wingnuts (except in particularly dry environments) but are lighter and will not corrode over time. Anderson Plugs are built with durability in mind and will remain easy to tighten and leak-free even after years of use. Straight sided rubber is the best choice for accurate, safe pressure testing in swimming pool plumbing lines, but it’s important to choose the correct sized plug. We recommend choosing a plug size that is about 1/8” smaller than the inside diameter of the pipe opening you are plugging off. The measurement listed for each size is the actual diameter of the unexpanded rubber.