The bean bags are, as you right said, made out of cloth. They are usually 6" x 3" and fiiled with beans. The amount of beans depends who is going to use them and what for. Obviously if they are for children, fewer beans and less weight is more desirable. If they are for adults - go for it.
I have found, through research that bags are 6 X 6 filled with either beans or kernel corn. Cloth of any kind as long as it is durable.