Prevue Pet Products' Medium Grass Hut is a natural, woven grass activity center for small animals, such as chinchillas and guinea pigs. Designed to satisfy their natural instincts to burrow, explore and nest, the 11-in. x 9-in. x 6-in. huts are 98 percent sisal tassel, .75 percent plant cane, .75 percent bamboo and .5 percent sisal rope, according to the manufacturer.