Bakhtiari carpets are based on a cotton foundation with a wool weft usually taken from the herds of the producing tribe. This leads to unique carpets that differ depending on the characteristics of each tribe's wool. The wool can range from dull to extreme glossy and the resultant pile is clipped medium to high. The best carpets with the highest knot density are often known as Bibibaff. Prices range considerably with the highest knot density rugs generally being the most expensive, but the price is also affected by criteria such as the pattern and the dyes used. Chapel Shotur and Saman pieces are rated slightly beneath Bibibaff productions but are still considered to be good to excellent. Hori carpets are of looser weave and inferior quality and as such, are generally widely affordable.