The original denim fabric used by Levi’s for production of their 501 jeans. According to the legend, the name 501 itself derived from the lot number of this fabric. Cone Mills South Carolina delivers XX-denim and only to Levi Strauss. It was a Gentlemen agreement 100 years ago between Levi’s himself and Cone Mills. Only a handshake was done, no contracts, and it is still valid. The model 501 jean, XX denim is probably the strongest denim you find unless there are smaller quantities of very expensive special made fabric.