The numbers marked on the plastic materials represent the material from which the product is produced. If there is no sign on the plastic product you bought, you should definitely stay away from this plastic. Most of us have seen the numbers written on or under the plastics that we use frequently in our daily lives, even without knowing whether the material used is reusable or not, but we have not questioned what it means. On the bottom or top of all plastic bottles, carboys, cans, there is usually a triangle-like logo inside a number showing the material the bottle is made of. These numbers range from 1 to 7 and are very important.