Convenient, Practical & Leakproof Plugs: The BOPOREAE Rubber Scupper Plug is a twist/turn pipe plug for a leak proof seal; The Premium Stainless Steel and Nitrile Butadiene Rubber (NBR) construction makes this test plug resists heat, anti-freeze, oil and rust inhibitors, wear-resistant, wet-dry versatile and airtight; Sturdy and Durable, Not Easy To Deform.