Possibly the most common form of fiberization, rotary fiberization utilizes centrifugal force to form fibers. A hollowed wheel with many small holes is injected with whatever molten material is being fiberized. The wheel must by necessity include vents for the hot gases as well. One design for rotary fiberization places slits in a central bore-axle that lets the hot gases escape. As the centrifugal force squeezes the molten material out of the holes, it is severed from the wheel by a sharpblade. As the fibers are collected, several post-processes can be applied, such as grouping or bunching.