Rolls of written prayers, or mantras, are sealed inside the cylinder, which is spun with a flick of the wrist. Spinning the wheel brings the same benefits as reading the respective texts and each cycle counts as one repetition of the prayer. As many as forty thousand prayers can be tightly rolled up in the cylinder, so within a few minutes millions of mantras can be 'sent out', and the wheel may be spun for hours.
There are various kinds of prayer wheel in Tibet. Some are placed on the roofs of houses and turned by the wind; others are powered by running water in rivers and streams, or spun by the hot air rising from lamps and stoves. Large prayer wheels stand in the entrances of temples and are spun by visiting devotees. Together, they radiate endless blessings into the environment: just to be struck by a wind that has touched a prayer wheel cleanses sins and clears obstacles to enlightenment. The spread of new technologies has also led to the development of a more technically advanced method for making a prayer wheel: you can now download mantras onto your computer's hard drive, where it will spin at fifty-four hundred rotations per minute.