This is a 100% plastic free double walled stainless steel bottle which can keep water hot/cold for more than 18 hours; made up of 304 Stainless Steel which is a type of Food grade steel that is highly durable , resitant to corrosion , hence a great choice for storing food items / water or beverages. Copper bottles tend to get stained as they react with different substances , but steel bottles are resistant to that.Also Steel utensils are known to last 10 years or more! It won't dent easily , highly resistant to corrosion as well. This is BPA free & BPS free Overall a great bottle!