Hello, my friend wants me to buy the original stock of automobile exhaust purifier. How to check the authenticity of this matter? How to prevent being cheated? Thank you, teacher.

Don't buy it. The car mechanic has closed down. I bought it at first, but later I bought it small. When I go back, I can exchange points for a car. I was fine at first, but then I started to refund my money, saying that I was much older. Later, I submitted my application for retirement, but it didn't pass at all. It has been shown that I still haven't brought back more than 1000.