If it is the original fabric is not easy to see, generally after washing can better distinguish the pros and cons of fabric!
First of all, look at the color, good gloss, bright color, smooth cloth surface, generally after mercerizing treatment, good quality.
Look at the yarn count and composition, cotton is more expensive than polyester cotton, but cotton is more expensive. The thin one is more expensive than the thick one.
If it's elastic denim, it's more expensive than the elastic yarn produced by other companies, and the elasticity is more lasting!
The last is whether it is fashionable or not. People who are very familiar with denim can sweep all good denim with their eyes. It's worth learning!