These Persian carpets are between the best carpets in the world. One of the most famous is the Nain Habibian but because they are in high demand there are many quality imitations in India and Pakistan. The Nain carpets are also using a different measurement of knot density called "laa". This refers to the number of threads and determines the quality of Nain carpet. There are three qualities: 9 laa, 6 laa and 4 laa. The most expensive are the 4 laa Nain.