Bakhtiari oriental rugs woven before 1950 were examples of tribal rugs, which are traditionally smaller rugs, with wool yarns hand knotted onto a wool foundation. The nomadic lifestyle of these sheep herding tribes, moving their stock from winter to summer pasture, dictated the necessity of smaller and easily movable looms, using the wool from their sheep for the foundation and pile of their rugs. Sometime in the middle of the last century, these nomadic tribes began to settle in various villages in Western persia. Weaving looms that did not have to be seasonally moved could be larger and sturdier, making the production of larger size rugs possible. The use of cotton for the foundation of the rugs also became more and more common. Baktiari rugs woven today use wool pile knotted on cotton foundations. Generally speaking, Bakhtiari rugs are made of very good wool with the knots thoroughly beaten down to make the rugs thick and solid. They are considered to be one of the most durable and long-lasting of Persian rugs.