As long as it is a regular manufacturer's products, there should be no design flaws. Low-quality products are often the result of the manufacturing process using shoddy parts, or rough processing. Rubber products are afraid of oil, and sometimes also due to other dust impurities and other factors cause the rubber ring seal is not tight. In addition, even if it is a high-quality products, may also appear in some parts of the suction is not firm condition.