Two types of Pressure Casting are typically employed in wheel construction, Low-Pressure Casting and Counter-Pressure Casting. In terms of quality and strength, the results are similar between both processes, and are a significant improvement over Gravity Casting. Most OEM wheels are manufactured using Pressure Casting.Low-Pressure Casting uses air pressure to force the molten alloy into the wheel mold. This causes the molten alloy to pack itself more densely.Counter-Pressure Casting uses a similar, but opposing process. It involves creating a mild vacuum by which the molten alloy is literally sucked into the wheel mold.