Counter-pressure is best described as an operation extension of the standard injection molding process. The difference is how we are able to control the melt front of the incoming resin during resin injection. Molten plastic injected into a typical mold will flow in the path of least resistance. In other words, nominal walls fill first and then thinner walls or features are filled and packed nearer the end of the injection sequence. Counter-pressure provides a controlled resistance to the flow front, forcing some of the melt to enter the thinner or harder to fill areas during the initial injection.