Fillers are chosen on the basis of comfort, resilience, cost and to a lesser extent for ethical and health reasons. The most common synthetic fillers are foam, synthetic plastic fibers (typically polyester) and viscoelastic foam and latex. Synthetic fillers are more common as they are comfortable, inexpensive and retain their form longer. Natural fillers have been used since antiquity. The most common are feathers, or down, wool, cotton(particularly in India), buckwheat (in Asia). Historically, materials have included straw, wood or stone. Feathers and down are usually the most comfortable and common; they offer the advantage of softness and their ability to conform to shapes desired by the user, but are the most expensive. Down has been known to be plucked from live geese. There are currently hypoallergenic and cruelty-free varieties of down pillows to allow people sensitive to down to enjoy the comfort of feather or down pillows. In India, traditional pillows are usually made with plant-borne materials, such as the fluffy, glossy fruit-fibres of silk-cotton tree (Ceiba pentandra and Bombax ceiba).