An air caster is a pneumatic lifting device used to move heavy loads on flat, non-porous surfaces. Its operation is similar to a hovercraft, as it uses a thin layer of air as a way to float a very small distance off the ground. Compressed air enters an airbag shaped like a torus, and when the bag is filled it creates an airtight seal with the ground, and forces more air into the center of torus, eventually causing the air to flow over the bag and to raise the load above the ground. The compressed air is forced under the airbag, pushing it and the load less than a millimeter off the ground.