Water-assisted injection moulding is the latest way to produce hollow or semi-hollow objects. The process is similar to gas-assisted injection moulding in that only part of the mould cavity is filled with plastic and the slurry is then pressed into the mould cavity with water (or high-pressure inert gas in the case of gas-assisted moulding), thus producing a hollow product. The great advantage of water assisted technology (WIT) is that it cools the material directly from the inside.