At the front of the barrel, the molten plastic leaves the screw and travels through a screen pack to remove any contaminants in the melt. The screens are reinforced by a breaker plate (a thick metal puck with many holes drilled through it) since the pressure at this point can exceed 5,000 psi (34 MPa).
Prior to exiting the barrel, molten plastic is filtered through a screen pack and then encounters a reinforced breaker plate, a sturdy metal disk with many holes, to withstand pressures of up to 5,000 psi (34 MPa) at this point.